Nonvolatile memory device, nonvolatile memory system, and access device having a variable read and write access rate

The present invention relates to: a nonvolatile memory device having a semiconductor memory such as a semiconductor memory card; an access device for accessing the nonvolatile memory device; and a nonvolatile memory system including them.

A nonvolatile memory device having a rewritable nonvolatile memory is increasingly demanded mainly for a semiconductor memory card. The semiconductor memory card is high-price compared to an optical disk, a tape medium, and the like. The semiconductor memory card, however, is increasingly demanded as a recording medium for a portable apparatus such as a digital still camera and a mobile phone because of merits such as small-size, lightweight, vibration resistance, and easy handling, and is used for not only a consumer-use moving image recording apparatus but also a professional-use moving image recording apparatus. In addition, not only the portable apparatus but also a stationary apparatus such as a digital television and a DVD recorder include a slot for the semiconductor memory as standard equipment. Thus, still images shot with the digital still camera can be browsed on the digital television, and moving images shot with the consumer-use moving image recording apparatus can be dubbed to the DVD recorder.

The semiconductor memory card includes a flash memory as a nonvolatile main memory, and has a memory controller for controlling it. The memory controller controls data reading and data writing to the flash memory in accordance with data reading and data writing commands from an access device such as a digital still camera.

In these years, needs for a large capacity semiconductor memory card is grown to store AV contents of highly-improved quality such as a still image and a moving image, that is, a large capacity of data size of one content. According to this, when an AV content recorded in the semiconductor memory card is dubbed to a recording medium such as a hard disk or DVD recorder incorporated in a hard disk recorder and a personal computer, a performance able to read data from the semiconductor memory at a higher speed is required. In addition, when an AV content recorded in the recording medium such as the hard disk is dubbed to the semiconductor memory card, a performance able to write data to the semiconductor memory at a higher speed is required. That is, it becomes important from now to reduce a waiting time of user by dubbing the recorded data at a high speed between the recording medium.

Conventional techniques for controlling the high speed data reading and writing in the semiconductor memory card are: a technique of a parallel access of a flash memory shown in Patent document 1; and a technique for speeding up a bus to connect a semiconductor memory card to an access device shown in Patent document 2.

However, when data is read or written at a high speed, surface temperatures of a host device and a semiconductor memory card become exceedingly high in general, and thereby a user is at a risk of a burn when ejecting the semiconductor memory card from the host device. Patent document 3 discloses a conventional technique for detecting and controlling such heat generation. This technique prevents increase of temperature by detecting: a temperature of an MPU; and opening and closing conditions of a lid of a connector and by switching an operation clock of the MPU.

Patent document 1: Japanese Unexamined Patent Publication No. 2000-510634 Patent document 2: Japanese Unexamined Patent Publication No. 2003-223623 Patent document 3: Japanese Unexamined Patent Publication No. H09-237129

Problems to be Solved by the Invention

However, when data reading and writing are frequently carried out at a high speed, a surface temperature of a semiconductor memory card increases mainly because of heat generation of the flash memory, thereby a user is at a risk of a burn when ejecting the semiconductor memory card from the host device.

Additionally, in the technique disclosed in Patent document 3, an operation clock is switched only based on opening and closing conditions of the lid of the connector. Thus, when a nonvolatile memory device such as the semiconductor memory card is inserted in a lidless connecter and the data reading and writing are carried out at a high speed, an operation clock of an MPU cannot be appropriately switched, thereby the heat generation cannot be suppressed. In addition, since a relation between an access rate and a temperature change of the nonvolatile memory device is not considered, it is impossible to set an appropriate access rate. Moreover, in a case of recording a moving image, it is generally unacceptable that the recording stops in midstream, however, since the technique disclosed in Patent document 3 is not able to set an appropriate access rate based on the relation with the temperature change, there is a possibility that the recording stops due to the heat generation.

In view of the above-mentioned problems, the present invention intends to provide a nonvolatile memory device, a host device, and a nonvolatile memory system that can eliminate a risk of a burn by suppressing heat generation and can write and read data at a high speed.

Means to Solve the Problems

To solve the problems, a nonvolatile memory of the present invention which reads and writes data in accordance with an access command from an outside device, the nonvolatile memory device includes: a nonvolatile memory for storing data; and a memory controller for reading and writing data from and to the nonvolatile memory, wherein the memory controller has an access rate control part for controlling an access rate for data reading or writing in accordance with an operating condition of the nonvolatile memory device in the data reading or writing.

The operating condition may be a temperature of the nonvolatile memory device; and the access rate control part may include: a temperature detection part for detecting the temperature of the nonvolatile memory device; and a temperature-adaptive control part for: retaining a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature; interrupting an access when a temperature detected by the temperature detection part rises higher than the first threshold temperature; and resuming the access when the temperature detected by the temperature detection part falls below the second threshold temperature.

The temperature-adaptive control part of the access rate control part may retain a third threshold temperature that indicates a temperature near a dangerous temperature for handling the nonvolatile memory device and control an access rate so as to lower the access rate when the temperature detected by the temperature detection part rises higher than the third threshold temperature.

The temperature detection part may include a temperature sensor.

The access rate control part may include a status information generation part for: generating status information representing a status of the nonvolatile memory device; and notifying the outside device of the status information.

The status information may be information representing a temperature of the nonvolatile memory device.

The status information may be warning information showing that a temperature of the nonvolatile memory device is higher than the first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device.

The status information may be access rate control execution information showing whether or not the access rate control is executed.

The status information may be a reading-writing allowable time representing time for which a temperature of the nonvolatile memory device reaches the first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device from that of a beginning of access.

The status information may be a reading-writing allowable size representing a data size that can be read and written from and to the nonvolatile memory device until a temperature of the nonvolatile memory device reaches the first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device.

The operating condition may be a temperature of the nonvolatile memory device; and the access rate control part may include: a temperature calculation part for calculating the temperature of the nonvolatile memory device by employing an access rate and time for which data is read or written at the access rate from and to the nonvolatile memory device as variables; and a temperature-adaptive control part for: retaining a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature; interrupting an access when a temperature detected by the temperature detection part rises higher than the first threshold temperature; and resuming the access when the temperature detected by the temperature detection part falls below the second threshold temperature.

The temperature-adaptive control part of the access rate control part may retain a third threshold temperature that indicates a temperature near a dangerous temperature for handling the nonvolatile memory device and control an access rate so as to lower the access rate when the temperature detected by the temperature detection part rises higher than the third threshold temperature.

The operating condition may be a data size for an access to the nonvolatile memory device; and the access rate control part may be a data size adaptive access rate control part for: determining an access rate on the basis of the data size so that the nonvolatile memory device cannot exceed a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device; and notifying the outside device of the access rate.

The operating condition may a temperature of the nonvolatile memory device; and the access rate control part may include: a temperature retention part for retaining the temperature of the nonvolatile memory device provided from the outside device; and a temperature-adaptive control part for: retaining a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature; interrupting an access when a temperature retained in the temperature retention part rises higher than the first threshold temperature; and resuming the access when the temperature retained in the temperature retention part falls below the second threshold temperature.

The temperature-adaptive control part of the access rate control part may retain a third threshold temperature that indicates a temperature near a dangerous temperature for handling the nonvolatile memory device and control an access rate so as to lower the access rate when the temperature retained in the temperature retention part rises higher than the third threshold temperature.

The operating condition may be a temperature of the nonvolatile memory device; and the access rate control part may include: a temperature calculation part for: setting a temperature of the nonvolatile memory device provided from the outside device to be an environmental temperature at a beginning of access; and calculating the temperature of the nonvolatile memory device on the basis of the environmental temperature and an accessing period; and a temperature-adaptive control part for: retaining a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature; interrupting an access when a temperature calculated by the temperature calculation part rises higher than the first threshold temperature; and resuming the access when the temperature calculated by the temperature calculation part falls below the second threshold temperature.

The temperature-adaptive control part of the access rate control part may retain a third threshold temperature that indicates a temperature near a dangerous temperature for handling the nonvolatile memory device and control an access rate so as to lower the access rate when the temperature calculated by the temperature calculation part rises higher than the third threshold temperature.

To solve the problems, a nonvolatile memory system of the present invention includes: an access device; and a nonvolatile memory device which reads and writes data in accordance with an access command from the access device, wherein the nonvolatile memory device includes: a nonvolatile memory for storing data; and a memory controller for reading and writing data from and to the nonvolatile memory, the memory controller having an access rate control part for controlling an access rate for data reading or writing in accordance with an operating condition of the nonvolatile memory device in the data reading or writing.

The operating condition may be a temperature of the nonvolatile memory device; and the access rate control part may include: a temperature detection part for detecting the temperature of the nonvolatile memory device; and a temperature-adaptive control part for: retaining a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature; interrupting an access when a temperature detected by the temperature detection part rises higher than the first threshold temperature; and resuming the access when the temperature detected by the temperature detection part falls below the second threshold temperature.

The temperature-adaptive control part of the access rate control part may retain a third threshold temperature that indicates a temperature near a dangerous temperature for handling the nonvolatile memory device and control an access rate so as to lower the access rate when the temperature detected by the temperature detection part rises higher than the third threshold temperature.

The temperature detection part may include a temperature sensor.

The access rate control part may include a status information generation part for: generating status information representing a status of the nonvolatile memory device; and notifying the access device of the status information.

The operating condition may be a temperature of the nonvolatile memory device; and the access rate control part may include: a temperature calculation part for calculating the temperature of the nonvolatile memory device by employing an access rate and time for which data is read and written at the access rate from and to the nonvolatile memory device as variables; and a temperature-adaptive control part for: retaining a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature; interrupting an access when a temperature detected by the temperature detection part rises higher than the first threshold temperature; and resuming the access when the temperature detected by the temperature detection part falls below the second threshold temperature.

The temperature-adaptive control part of the access rate control part may retain a third threshold temperature that indicates a temperature near a dangerous temperature for handling the nonvolatile memory device and control an access rate so as to lower the access rate when the temperature detected by the temperature detection part rises higher than the threshold temperature.

The operating condition may be a data size for an access to the nonvolatile memory device; and the access rate control part may be a data size adaptive access rate control part for: determining an access rate on the basis of the data size so that the nonvolatile memory device cannot exceed a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device; and notifying the access device of the access rate.

The operating condition may be a temperature of the nonvolatile memory device; and the access rate control part may include: a temperature retention part for retaining the temperature of the nonvolatile memory device provided from the access device; and a temperature-adaptive control part for: retaining a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature; interrupting an access when a temperature retained in the temperature retention part rises higher than the first threshold temperature; and resuming the access when the temperature retained in the temperature retention part falls below the second threshold temperature.

The temperature-adaptive control part of the access rate control part may retain a third threshold temperature that indicates a temperature near a dangerous temperature for handling the nonvolatile memory device and control an access rate so as to lower the access rate when the temperature retained in the temperature retention part rises higher than the third threshold temperature.

The operating condition may be a temperature of the nonvolatile memory device; and the access rate control part may include: a temperature calculation part for: setting a temperature of the nonvolatile memory device provided from the access device to be an environmental temperature at a beginning of access; and calculating the temperature of the nonvolatile memory device on the basis of the environmental temperature and an accessing period; and a temperature-adaptive control part for: retaining a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature; interrupting an access when a temperature calculated by the temperature calculation part rises higher than the first threshold temperature; and resuming the access when the temperature calculated by the temperature calculation part falls below the second threshold temperature.

The temperature-adaptive control part of the access rate control part may retain a third threshold temperature that indicates a temperature near a dangerous temperature for handling the nonvolatile memory device and control an access rate so as to lower the access rate when the temperature calculated by the temperature calculation part rises higher than the third threshold temperature.

The access device may include a temperature information output part for: reading a value of temperature detected by a temperature sensor in the access device; and supplying the read value as temperature information in the access device to the nonvolatile memory device with a flag indicating that the access device has the temperature sensor.

The temperature information output part may supply the temperature detected by the temperature sensor in the access device to the nonvolatile memory device with a flag indicating that the detected temperature is either one of a temperature and an environmental temperature of the nonvolatile memory device.

To solve the problems, a nonvolatile memory system of the present invention includes: an access device; and a nonvolatile memory device which is connected to the access device and reads and writes data in accordance with an access command from the access device, wherein: the nonvolatile memory device has: a nonvolatile memory for storing data; and a memory controller for reading and writing data from and to the nonvolatile memory, the memory controller including a register part for: retaining a temperature parameter including a temperature increasing speed of the nonvolatile memory device and a saturate temperature to which an increasing temperature of the nonvolatile memory device converges; and outputting the temperature parameter to the access device; and the access device has: a temperature detection part for detecting the temperature of the nonvolatile memory device; and an access rate control part for: calculating a temperature change of the nonvolatile memory device caused by a data transfer for each access rate included in the access device by using the temperature parameter obtained from the nonvolatile memory device and the temperature of the nonvolatile memory device detected by the temperature detection part; and accessing the nonvolatile memory device at an access rate at which the temperature of the nonvolatile memory device cannot exceed a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device.

To solve the problems, a nonvolatile memory system of the present invention includes: an access device; and a nonvolatile memory device which is connected to the access device and reads and writes data in accordance with an access command from the access device, wherein: the nonvolatile memory device has: a nonvolatile memory for storing data; and a memory controller for reading and writing data from and to the nonvolatile memory in accordance with a command from the access device; and the access device has: a temperature detection part for detecting the temperature of the nonvolatile memory device; a temperature parameter retention part for retaining a temperature parameter including a temperature increasing speed of the nonvolatile memory device and a saturate temperature to which an increasing temperature of the nonvolatile memory device converges; and an access rate control part for: calculating a temperature change of the nonvolatile memory device caused by a data transfer for each access rate retained in the access device by using the temperature parameter retained by the temperature parameter retention part and the temperature of the nonvolatile memory device detected by the temperature detection part; and accessing the nonvolatile memory device at an access rate at which the temperature of the nonvolatile memory device cannot exceed a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device.

The temperature parameter of the register part further may include a temperature decreasing speed of the nonvolatile memory device of a case where an access is not carried out; and the access rate control part may interrupt a data transfer when the temperature of the nonvolatile memory device reaches the first threshold temperature corresponding to the access rate retained by the access device on the basis of the temperature information and the temperature of the nonvolatile memory device detected by the temperature detection part, determine the continuous access allowable time in resuming the data transfer on the basis of a temperature change of the nonvolatile memory device when the temperature of the nonvolatile memory device falls to a second threshold temperature that is a criterion used for resuming the data transfer, and access the nonvolatile memory on the basis of the determined access allowable time.

The access rate control part may control an access rate by changing a clock frequency used for the writing and reading of data.

The access rate control part may control an access rate by changing an interval between periods where data of a predetermined unit are transferred.

The access device may further include a codec part for generating compressed data of moving image data; and the access rate control part may determine an access rate by changing a data transfer speed of the compressed data generated by the codec part.

The access rate control part may determine an access rate by changing a bit rate of the compressed data generated by the codec part.

The access rate control part may determine an access rate by changing a frame rate of the compressed data generated by the codec part.

To solve the problem, an access device of the present invention which writes data to a nonvolatile memory device and reads data from the nonvolatile memory device, includes: a display part for displaying information related to the access device; and a control part for displaying status information showing a state of the nonvolatile memory device notified from the nonvolatile memory device.

To solve the problems, an access device of the present invention which writes data to a nonvolatile memory device and reads data from the nonvolatile memory device, includes: a cooling part for cooling the nonvolatile memory device; and a control part for driving the cooling part on the basis of status information showing a state of the nonvolatile memory device notified from the nonvolatile memory device.

The control part may retain a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device and a second threshold temperature that is a safe temperature lower than the first threshold temperature, compare a temperature of the nonvolatile memory device that is the status information notified from the nonvolatile memory device with the first threshold temperature and the second threshold temperature, drive the cooling part when the temperature is higher than the first threshold temperature, and stop the cooling part when the temperature is lower than the second threshold temperature.

The control part may drive the cooling part only for a predetermined period when warning information showing the temperature exceeds the first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device is notified.

The control part may drive the cooling part only for a predetermined time when the access rate control information is notified as the status information and the access rate control information shows that an access rate is lowered.

The control part may retain a threshold time for the reading and writing of data and drive the cooling part only for a predetermined time when a reading-writing allowable time is notified as the status information and the notified reading-writing allowable time is shorter than the threshold time.

The control part may retain a threshold size of data size to be read and written and drive the cooling part only for a predetermined time when a reading-writing allowable size is notified as the status information and the notified reading-writing allowable size is shorter than the threshold size.

To solve the problem, an access device of the present invention which writes data to a nonvolatile memory device and reads data from the nonvolatile memory device, includes: a temperature detection part for detecting the temperature of the nonvolatile memory device; and an access rate control part for: calculating a temperature change of the nonvolatile memory device caused by a data transfer for each access rate included in the access device by using the temperature parameter obtained from the nonvolatile memory device and the temperature of the nonvolatile memory device detected by the temperature detection part; and accessing the nonvolatile memory device at an access rate at which the temperature of the nonvolatile memory device cannot exceed a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device.

To solve the problem, an access device of the present invention which writes data to a nonvolatile memory device and reads data from the nonvolatile memory device, includes: a temperature detection part for detecting the temperature of the nonvolatile memory device; a temperature parameter retention part for retaining a temperature parameter including a temperature increasing speed of the nonvolatile memory device and a saturate temperature to which an increasing temperature of the nonvolatile memory device reaches; and an access rate control part for: calculating a temperature change of the nonvolatile memory device caused by a data transfer for each access rate retained in the access device by using the temperature parameter retained by the temperature parameter retention part and the temperature of the nonvolatile memory device detected by the temperature detection part; and accessing the nonvolatile memory device at an access rate at which the temperature of the nonvolatile memory device cannot exceed a first threshold temperature that is the lower limit of temperature dangerous for handling the nonvolatile memory device.

The temperature parameter obtained from the nonvolatile memory device may further include a temperature decreasing speed of the nonvolatile memory device of a case where an access is not carried out; and the access rate control part may interrupt a data transfer when the temperature of the nonvolatile memory device reaches the first threshold temperature corresponding to the access rate retained by the access device on the basis of the temperature information and the temperature of the nonvolatile memory device detected by the temperature detection part, determine the continuous access allowable time in resuming the data transfer on the basis of a temperature change of the nonvolatile memory device when the temperature of the nonvolatile memory device falls to a second threshold temperature that is a criterion used for resuming the data transfer, and access the nonvolatile memory on the basis of the determined access allowable time.

The access rate control part may control an access rate by changing a clock frequency used for the writing and reading of data.

The access rate control part may control an access rate by changing an interval between periods where data of a predetermined unit is transferred.

The access device may further include a codec part for generating compressed data of moving image data; and the access rate control part may determine an access rate by changing a data transfer speed of the compressed data generated by the codec part.

The access rate control part may determine an access rate by changing a bit rate of the compressed data generated by the codec part.

The access rate control part may determine an access rate by changing a frame rate of the compressed data generated by the codec part.

Effectiveness of the Invention

In a nonvolatile memory device and a nonvolatile memory system of the present invention, an access rate control part in the nonvolatile memory device controls an access rate on the basis of a temperature of the nonvolatile memory device or a size of all data to be read and written and cools the nonvolatile memory device, thereby data reading and writing can be carried out at a high speed with temperature increase of the nonvolatile memory device in reading and writing data from and to a nonvolatile memory suppressed so that a user cannot be at a risk of a burn.

In an access device of the present invention, the data reading and writing can be carried out at a high speed with temperature increase of the nonvolatile memory device caused by reading and writing data from and to the nonvolatile memory suppressed so that a user cannot be at a risk of a burn. In addition, since an access rate is controlled by switching a bit rate or a frame rate in a case of recording a moving image, it is possible to prevent the recording from being stopped due to heat generation.

FIG. 1 is a block diagram showing a nonvolatile memory system according to a first embodiment of the present invention.

FIG. 2 is a memory map of a buffer 102 .

FIG. 3 is a block diagram showing a nonvolatile memory 120 .

FIG. 4 is a configuration view of a physical block of the nonvolatile memory 120 .

FIG. 5 is a time chart showing an operation of data writing of an access device 200 A.

FIG. 6 is a flowchart showing an operation of writing of a memory controller 110 A.

FIG. 7 is a time chart of a high-speed access showing the writing to the nonvolatile memory 120 without controlling the access rate.

FIG. 8 is a graph showing a temperature change of a nonvolatile memory device 100 A.

FIG. 9 is a time chart of a low-speed access showing the writing to the nonvolatile memory 120 without controlling the access rate.

FIG. 10 is a time chart showing the writing to the nonvolatile memory 120 with an access rate controlled.

FIG. 11 is a graph showing the temperature change of the nonvolatile memory device 100 A.

FIG. 12 is a block diagram showing a nonvolatile memory system according to a second embodiment of the present invention.

FIG. 13 is a time chart showing an operation of data writing of an access device 200 B.

FIG. 14 is a flowchart showing an operation of writing of a memory controller 110 B.

FIG. 15 is a block diagram showing a nonvolatile memory system according to a third embodiment of the present invention.

FIG. 16 is a block diagram showing a nonvolatile memory system according to a fourth embodiment of the present invention.

FIG. 17 is a time chart showing an operation of data writing of an access device 200 D.

FIG. 18 is a flowchart showing an operation of writing of a memory controller 110 D.

FIG. 19 is a block diagram showing a nonvolatile memory system according to a fifth embodiment of the present invention.

FIG. 20 is a graph showing a temperature change of a nonvolatile memory device.

FIG. 21 is a block diagram showing a nonvolatile memory system according to a sixth embodiment of the present invention.

FIG. 22 is a graph showing a temperature change of a nonvolatile memory device 200 E with an access rate controlled.

FIG. 23 is a graph showing a temperature change of the nonvolatile memory device 200 E.

FIG. 24 is a graph showing a temperature change of the nonvolatile memory device 200 E with the access rate controlled.

FIG. 25 is a block diagram showing a nonvolatile memory system according to a seventh embodiment of the present invention.

FIG. 26A is a configuration view of temperature information according to the seventh embodiment of the present invention.

FIG. 26B is a configuration view of the temperature information according to the seventh embodiment of the present invention.

FIG. 27 is a view showing a state of a flag according to the seventh embodiment of the present invention.

FIG. 28 is a block diagram showing a nonvolatile memory system according to an eighth embodiment of the present invention.

FIG. 29 is a view showing a temperature parameter retained by a nonvolatile memory device 100 H.

FIG. 30 is a time chart showing access rate controls of an access device 200 H.

FIG. 31 is a time chart showing the access rate control of the access device 200 H.

FIG. 32 is a time chart showing temperature changes of the nonvolatile memory device 100 H.

FIG. 33 is a flowchart showing an access operation of the access device 200 H to the nonvolatile memory device 100 H.

FIG. 34 is a block diagram showing a nonvolatile memory system according to a ninth embodiment of the present invention.

FIG. 35 is a flowchart showing an access operation of the access device 200 I to the nonvolatile memory device 100 I.

FIG. 36 is a time chart showing temperature changes of a nonvolatile memory device 100 I.

FIG. 37 is a block diagram showing a nonvolatile memory system according to a tenth embodiment of the present invention.

FIG. 38A is a view showing moving image recording modes provided to a codec part 217 .

FIG. 38B is a view showing the moving image recording modes provided to the codec part 217 .

100 A, 100 B, 100 C, 100 D, 100 E, 100 F, 1000 , 100 H Nonvolatile Memory Device

110 A, 110 B, 110 C, 110 D, 110 E, 110 F, 110 G, 110 H Memory Controller

101 Host interface

102 Buffer

103 Reading-writing control part

104 CPU

105 Address management part

106 A, 106 B, 106 C, 106 E, 106 F, 106 G, 117 Access rate control part

111 , 117 Temperature detection part

112 Temperature-adaptive control part

113 Status information generation part

114 , 116 Temperature calculation part

115 Temperature retention part

120 Nonvolatile memory

130 Mode changeover switch

200 A, 200 B, 200 C, 200 D, 200 E, 200 F, 200 G, 200 H, 200 I, 200 J Access device

201 Display part

202 , 203 , 205 , 209 Control part

204 Cooling part

206 Temperature output part

207 A, 207 B Environmental temperature output part

208 Temperature information output part

211 System control part

212 , 217 Codec part

213 ROM and RAM

214 Display part

215 Display control part

216 H, 216 I, 216 J Nonvolatile memory device control part

221 Memory device access part

222 Temperature detection part

223 , 225 Access rate control part

224 Temperature parameter retention part

300 to 315 Flash memory

320 to 323 Memory bus

First Embodiment

FIG. 1 is a block diagram showing a nonvolatile memory system according to a first embodiment of the present invention. As shown in FIG. 1 , the nonvolatile memory system of the present embodiment is configured by including a nonvolatile memory device 100 A and an access device 200 A to which the nonvolatile memory device 100 A is attached.

Firstly, the access device 200 A includes: a display part 201 for displaying information related to the nonvolatile memory system; and a control part 202 . The control part 202 accesses the nonvolatile memory device 100 A to write and read data, and carries out a control to display necessary information of information received from the nonvolatile memory device 100 A.

Next, the nonvolatile memory device 100 A will be explained. As shown in FIG. 1 , the nonvolatile memory device 100 A includes a memory controller 110 A, a nonvolatile memory 120 that is a flash memory group, and a mode changeover switch 130 . The mode changeover switch 130 is a switching part for switching between an access rate control mode and a non access rate control mode that will be explained below.

The memory controller 110 A includes a host interface (host IF) 101 for communicating with the access device 200 A, a buffer 102 , a reading-writing control part 103 , a CPU 104 , an address management part 105 , and an access rate control part 106 A.

The buffer 102 is composed of, for example, a RAM having a size of 16 k bytes, and temporarily retains data transferred from the access device 200 A or data read from the nonvolatile memory 120 . FIG. 2 is a memory map showing the buffer 102 . The buffer 102 is configured by 8 regions from region 0 to region 7 each of which has a size of 2 k bytes. A writing pointer WP indicates a writing position of data transferred from the access device 200 A. Meanwhile, a reading pointer RP indicates a reading position where data is read from the buffer 102 .

The reading-writing control part 103 writes data temporarily retained by the buffer 102 to the nonvolatile memory 120 on the basis of a physical address designated by the address management part 105 . In addition, the reading-writing control part 103 reads data from the nonvolatile memory 120 and temporarily retains the read data in the buffer 102 .

The CPU 104 internally includes a programming ROM, a working RAM, and the like, and controls the whole of the memory controller 110 A.

The address management part 105 is a block for: converting a logical address transferred by the access from the access device 200 A into a physical address of the nonvolatile memory 120 ; and managing a recording status of the nonvolatile memory 120 and the like. Meanwhile, since a method for the address management can be realized by using a common technique, an explanation thereof will be omitted.

The access rate control part 106 A includes a temperature detection part 111 and a temperature-adaptive control part 112 . The temperature detection part 111 includes a temperature sensor such as a thermistor, and detects a temperature (hereinafter referred to as a temperature T) of the nonvolatile memory device 100 A.

The temperature-adaptive control part 112 for temperature adaptation stores a first and a second threshold temperatures in its internal ROM and the like. The first threshold temperature is a limit temperature (hereinafter referred to as a limit temperature Trisk) representing a lower limit of temperature at risk for a burn in handling the nonvolatile memory device. The second threshold temperature is a safe temperature (hereinafter referred to as a safe temperature Tsafe) that is lower than the first threshold temperature, is not at a risk of a burn, and can be determined to be sufficiently safe. The temperature-adaptive control part 112 works at any one of the access rate control mode and the non access rate control mode. The access rate control mode is for: comparing the temperature T measured by the temperature sensor with the limit temperature trisk or the safe temperature Tsafe; and interrupting data reading and data writing and changing an access rate on the basis of the comparison result. The non access rate control mode is for writing data in accordance with an access rate of the access device 200 A regardless of the temperature T without: interrupting data reading and data writing; and changing the access rate.

Subsequently, the nonvolatile memory 120 will be explained. FIG. 3 is a block diagram showing the nonvolatile memory 120 of the nonvolatile memory device 100 A. The nonvolatile memory 120 has 16 flash memories (FM) 300 to 315 , and is connected to the reading-writing control part 103 by using memory busses 320 to 323 .

FIG. 4 is a configuration view of a physical block included in each of the flash memories 300 to 315 . One flash memory includes a plurality of physical blocks, and one physical block has 128 pages which are writing units. Each page has a data region of 2048 bytes and a management region of 64 bytes. The data region of the physical block stores data transferred by the access device 200 A, and a management region of the first page marked with diagonal lines records a logical block number and a piece of physical management information which are created by the address management part 105 on the basis of a logical address transferred by the access device 200 A.

The data writing from the access device 200 A to the nonvolatile memory device 100 A in such configured nonvolatile memory system will be sequentially explained. FIG. 5 is a time chart showing a data transmission and a data reception of the access device 200 A in data writing. The access device 200 A firstly transmits a writing command to the nonvolatile memory device 100 A. Next, the access device 200 A sequentially transfers data to the nonvolatile memory device 100 A in units of 16 k bytes (cluster units). However, the access device 200 A interrupts the transfer of data while receiving busy information from the nonvolatile memory device 100 A. When the transfer of file data ends after such process, the access device 200 A transmits a transfer end command to the nonvolatile memory device 100 A.

Next, a flow of the data writing will be separately explained in the non access rate control mode and the access rate control mode. To simplify the description, in the present embodiment, only the data writing will be explained and an explanation of data reading will be omitted. FIG. 6 is a flowchart showing a control of the data writing carried out by the memory controller 110 A. In addition, to simplify the description, explanations of details which are not directly linked to the present invention and details which can be realized by using a general technique, for example, of system information stored in the nonvolatile memory 120 and a detailed operation of the address management part 105 are also omitted. Meanwhile, in the data writing, the access device 200 A sequentially writes data from logical address 0 in units of 16 k bytes.

[Data Writing Operation in Non Access Rate Control Mode]

At first, a process of data writing in the non access rate control mode that does not control an access rate will be explained. In FIG. 6 , an initializing operation at power-on is the same as that of a conventional memory controller. The address management part 105 firstly configures a logical-physical conversion table and the like in the address management part 105 on the basis of the logical block number and the physical management information recorded in the management region of each physical block of the flash memories 300 to 315 (S 100 ). In the writing of data from the access device 200 A that will be carried out later, the memory controller 110 A determines a physical address by using the logical-physical conversion table. The memory controller 110 A subsequently writes data temporarily retained in the buffer 102 to the flash memories 300 to 315 via the reading-writing control part 103 .

After the initializing processes at S 100 , the memory controller 110 A waits for a writing command for commanding the writing from the access device 200 A (S 101 ). When the memory controller 110 A receives the writing command from the access device 200 A, the CPU 104 passes a logical address transferred as an argument of the writing command to the address management part 105 . The address management part 105 determines a physical block on the basis of the logical address. Moreover, the CPU 104 makes the buffer temporarily retain data transferred following the writing command in accordance with the writing pointer WP and in ascending order from region 0 (S 102 ).

At a time when 2 kbyte-data has been retained in the buffer 102 , the reading-writing control part 103 reads temporarily-retained data from the buffer 102 in accordance with the reading pointer RP, and writes the read data to the nonvolatile memory 120 (S 103 ). Such processes at S 102 and S 103 are repeated till the amount of data transferred from the access device 200 A reaches 16 k bytes (S 104 ). Timings of the data transfer and writing in the access device 200 A, buffer 102 , and nonvolatile memory 120 , which are carried out at S 102 and S 103 , and temperature increase of the nonvolatile memory 120 will be described later.

After S 104 , the CPU 104 judges which mode has to be used, the access rate control mode or the non access rate control mode, based on a status of the mode changeover switch 130 (S 105 ). In the case of the non access rate control mode explained here, the process proceeds to S 109 .

The CPU 104 subsequently judges whether or not a transfer end command has been received from the access device 200 A (S 109 ). When the transfer end command has been received, the flow proceeds to step S 101 and the CPU waits for a next command. On the other hand, when the transfer end command has not been received, the flow proceeds to step S 102 and the process for writing data temporarily-retained in the buffer 102 to the nonvolatile memory 120 continues. The above is the explanation of data writing process in the non access rate control mode.

The timing of the data transfer and writing and the temperature increase of the nonvolatile memory 120 at S 102 and S 103 will be explained below. FIG. 7 is a time chart showing the data writing to the nonvolatile memory 120 without controlling an access rate in a case where a high-speed access is performed. FIG. 7 sequentially shows: the data transfer from the access device 200 A; the data reading from the buffer 102 ; and the data writing to each of the flash memories 300 to 315 . The numbers starting from 0 in the drawing are added to data transferred from the access device 200 A in units of 2 k bytes. Hereinafter, the data to which the number 0 is added is referred to as data 0 . In addition, the 8 units, for example, data 0 to data 7 represent 16 kbyte-data.

At first, data is transferred from the access device 200 A to the buffer 102 in the order from data 0 . Upon completion of the transfer of data 0 to the buffer 102 , the access device 200 A starts transferring data 1 , and at that time the reading-writing control part 103 starts reading data 0 from the buffer 102 . Specifically, FIG. 7 shows that the transfer of data 1 from the access device 200 A to the buffer 102 and the reading of data 0 from the buffer 102 are simultaneously carried out. Moreover, as shown in FIG. 7 , the reading-writing control part 103 transfers data 0 read from the buffer 102 to the flash memory 300 , and transfers data 1 to the flash memory 301 . In this manner, the writing data is transferred to the flash memories 300 to 315 in the order from data 0 .

In the sequence showing the writing to the flash memories 300 to 315 , a transfer period Pt (approximately 67 μS) without a hatched lines represents a period when the reading-writing control part 103 transfers writing data to an I/O register (not shown in the drawing) in the nonvolatile memory 120 via the memory bus. In addition, a writing period Pp (approximately 200 μS) with hatched lines represents a period when the flash memory writes data transferred to the I/O register to a page of a physical block. On this occasion, as shown in FIG. 7 , data is written in the order from the flash memory 300 to the flash memory 315 in units of 2 k bytes, and a circular writing is repeated. FIG. 7 further shows all of the flash memories 300 to 315 continue the data writing without ceasing.

When 8 kbyte-data is transferred at 67 μS from the access device 200 A in this manner, an access rate is approximately 120 Mbyte/S according to the following expression (1),

8 k bytes/67 μS≈120 Mbyte/S  (1).

A temperature increase of the nonvolatile memory device 100 A under such circumstances will be explained. A mainly-consumed power in the nonvolatile memory device 100 A is an electric power consumed in the transfer period Pt and the writing period Pp of the writing operation to the flash memories 300 to 315 . In the case where 16 flash memories 300 to 315 simultaneously operate constantly as shown in FIG. 7 , when power supply voltages of the flash memories 300 to 315 are 3.3V and consumed currents at Pt and Pp are 10 mA, a constant power consumption Q of the nonvolatile memory device 100 A is approximately 528 mW according to the following expression (2),

3.3V×10 mA×16=528 mW  (2).

Meanwhile, a power consumption of the memory controller 110 A realized by an integration circuit is sufficiently smaller than those of the flash memories 300 to 315 , and is ignored to simplify the calculation.

In the writing to the nonvolatile memories 300 to 315 , an average increased temperature ΔT of the nonvolatile memory device 100 A can be approximately calculated by the expression (3) quoted from “Masaru ISHIZUKA, et al., Countermeasures against heat and thermal simulation technology for downsizing and speeding-up electronic device, 1991”,

Δ T={Q /(1.78 ×S )} 0.8   (3).

Note that the Q is 0.528 W, a value of power consumption obtained by the expression (2). The S represents a surface area of the nonvolatile memory device 100 A. Here, when the nonvolatile memory device 100 A is an SD memory card, the surface area S is obtained by the following expression,

S ≈ ⁢ { ( 0.032 × 0.024 ) + ( 0.032 × 0.0021 ) + ( 0.024 × 0.0021 ) } × 2 = ⁢ 1.77 × 10 - 3 ⁢ ⁢ m 2 .

When this value S is used, ΔT is approximately 60° C. according to the expression (3).

Here, it can be understood that when a temperature around the nonvolatile memory device 100 A (hereinafter referred to an environmental temperature TE) is 25° C., the temperature T of the nonvolatile memory device 100 A increases to a summation of the environmental temperature TE and the increased temperature, namely, the temperature T=85° C. However, in a case of attaching the nonvolatile memory device 100 A inside the access device 200 A to use the memory device, since the environmental temperature TE is a temperature around the nonvolatile memory device 100 A, the environmental temperature is not necessarily 25° C. That is, the environmental temperature TE varies depending on a type of the access device 200 A, however, a quality standard used for manufacturing the nonvolatile memory device 100 A has been used here.

Then, FIG. 8 is a graph showing temperature changes of the nonvolatile memory device 100 A, and a temporal characteristic of the temperature T corresponding to the writing process at the above-mentioned high-speed access is represented by a solid line A of a graph of FIG. 8 . The temperature T at a start time of the writing is 25° C. that is the environmental temperature TE. After that, because of the writing of data, the temperature T gradually approaches a saturate temperature in an asymptotic manner obtained by adding the environmental temperature TE to the increased temperature ΔT calculated by the expression (3), that is, 85° C. here. Time required to increase to a rate of around 63% to the saturate temperature, namely, a thermal time constant varies depending on a way of access, a material, and the like of the nonvolatile memory device 100 A, however, it is, for example, an order of two or three minutes in a case of sequentially writing data to a certain memory card.

Next, using FIG. 9 , the writing process at a low-speed access will be explained. FIG. 9 is a time chart showing the data writing to the nonvolatile memory 120 in a case of not controlling an access rate, and shows a case where the low-speed access is carried out.

In FIG. 9 , an access rate of data transferred from the access device 200 A is approximately 60 Mbytes/S that is half as high as that of the case of high-speed access. In FIG. 9 , rates of: the transfer from the access device 200 A; and the reading from the buffer 102 are approximately half in comparison with the case of high-speed access. However, for example, the transfer period Pt of data 0 in the flash memory 300 is approximately 67 μS same as that of the case of high-speed access, and the writing period of data 0 is approximately 200 μS. FIG. 9 shows that when the access rate is reduced to half in this manner, a writing pausing period is generated in the same proportion as that of the writing period in each of the flash memories 300 to 315 . Meanwhile, the writing pausing period is a period when both of the data transfer and the data writing are not carried out. The power consumption value Q of the nonvolatile memory 120 is 264 mW that is around half as much as the power consumption at the high-speed access. When the nonvolatile memory device is an SD card, the increased temperature ΔT is approximately 35° C. as shown in the following expression (4),

Δ T={Q /(1.78 ×S )}0.8≈35° C.  (4).

It can be understood that the saturate temperature T becomes 60° C. by adding 25° C. of the environmental temperature to the above-mentioned increased temperature ΔT.

When the limit temperature Trisk is 60° C. here, a temporal characteristic of the temperature T corresponding to the writing process at the low-speed access is represented by a broken line B in the graph of FIG. 8 . The temperature T at a start time of writing is 25° C. that is the environmental temperature TE, and, after that, the temperature T gradually approaches the saturate temperature 60° C. in an asymptotic manner because of an electric power consumed by the writing process. As described above, in the case of low-speed access, the temperature does not exceed the limit temperature Trisk even when the data writing is perpetually carried out, as a result, it can be understood that there is no danger of a burn.

Meanwhile, FIG. 7 shows that the period when 8 kbyte-data is transferred from the access device 200 A and the buffer 102 and the period Pt take almost the same time, however, these periods are not necessarily the same. Similarly, in FIG. 9 shows that the period when 4 kbyte-data is transferred from the access device 200 A and the buffer 102 and the period Pt take almost the same time, however, these periods are not necessarily the same.

In addition, the access device 200 A may be configured so as to select the high-speed access or the low-speed access. For example, the device can make a decision so as to employ: the high-speed access for a high-speed continuous shooting mode of a digital still camera and the like; and the low-speed access mode for a normal shooting mode.

[Data Writing Operation in Access Rate Control Mode]

Next, using FIG. 6 , a data writing operation in the access rate control mode will be explained. Meanwhile, since S 100 to S 104 of FIG. 6 are the same as those of the above-mentioned data writing operation in the non access rate control mode, their explanations are omitted.

Following S 104 , the CPU 104 determines based on a state of the mode changeover switch 130 that the access rate mode is chosen (S 105 ). Then, the temperature-adaptive control part 112 compares the temperature T of the nonvolatile memory device 100 A detected by the temperature detection part 111 with the limit temperature Trisk (S 106 ).

When it is determined at S 106 that the temperature T is higher than the limit temperature Trisk, the temperature-adaptive control part 112 makes the reading-writing control part 103 interrupt the data writing and transmits busy information to the access device 200 A (S 107 ). The temperature-adaptive control part 112 judges whether or not the temperature T falls below the safe temperature Tsafe, transmitting the busy information (S 108 ). The flow returns to step S 107 when it has not been determined that the temperature T fell below the safe temperature Tsafe, and thus the busy information is transmitted until the temperature T falls below the safe temperature Tsafe at S 108 .

When it has been determined that the temperature T fell below the safe temperature Tsafe, the CPU 104 judges whether or not the memory controller 110 A received a transfer end command from the access device 200 A (S 109 ). When the transfer end command has been received, the flow proceeds to step S 101 and the CPU waits for next reading or writing command. Meanwhile, when the transfer end command has not been received, the flow proceeds to step S 102 and the writing of data temporarily retained in the buffer 102 to the nonvolatile memory 120 continues.

Next, using FIG. 10 and FIG. 11 , the temperature increase of the nonvolatile memory device 100 A in the access rate control mode will be explained. FIG. 10 is a time chart showing the data writing of the high-speed access in the above-mentioned access rate control mode. In FIG. 10 , data transfer is interrupted at time tr and the data transfer is resumed at time ts. In addition, FIG. 11 is a graph showing a temporal characteristic of the temperature T corresponding to the writing process of FIG. 10 . In FIG. 11 , the temperature T at writing start time t 0 is equal to 25° C. that is the environmental temperature TE, and, after that, the temperature T gradually rises in an asymptotic manner to 85° C. that is the saturate temperature because of an electric power consumed by the data writing. However, since the data transfer of the access device 200 A and the data writing of the reading-writing control part 130 are interrupted by the process of S 107 in FIG. 6 at the time tr when the temperature T exceeds the limit temperature Trisk, the temperature T begins to fall. The access device 200 A resumes data transfer and the reading-writing control part 130 resumes data writing at the time is when the temperature T falls below the safe temperature Tsafe, and the temperature T starts to rise again.

As described above, in the nonvolatile memory system shown in the present embodiment, when the temperature T of the nonvolatile memory device 100 A detected by the temperature detection part 111 exceeds the limit temperature Trisk, the temperature-adaptive control part 112 interrupts the writing operation of the reading-writing control part 103 and transmits busy information to the access device 200 A to make the access device 200 A interrupt the data transfer. In addition, when the temperature T has fallen below the safe temperature Tsafe, the data writing and the data transfer are resumed. In this manner, the access rate can be controlled, and a burn of user caused by the temperature increase of the nonvolatile memory device 100 A can be avoided also in the high-speed data writing.

Meanwhile, the temperature-adaptive control part 112 may retain data of a limit temperature Trisk 2 as a third threshold temperature lower than the limit temperature Trisk. This temperature Trisk 2 indicates a temperature near a dangerous temperature for handling the nonvolatile memory device, and is a temperature higher than the safe temperature Tsafe. When the temperature T exceeds this limit temperature Trisk 2 , the temperature-adaptive control part 112 switches the data writing of the reading-writing control part 103 from a high-speed access to a low-speed access.

Meanwhile, the data writing has been explained in the present embodiment, however, the access rate also can be controlled in the reading operation through the same process as the above-explained process. In addition, the limit temperature Trisk and the safe temperature Tsafe are determined on the basis of the quality standard used for manufacturing the nonvolatile memory device 100 A, and thus can take various values. Moreover, if the temperature detection part 111 is provided outside the memory controller 110 A, the same effect as that of the above-mentioned embodiment can be obtained.

Second Embodiment

FIG. 12 is a block diagram showing a nonvolatile memory system according to a second embodiment of the present invention. As shown in FIG. 12 , the nonvolatile memory system on the present embodiment is configured by including a nonvolatile memory device 100 B, and an access device 200 B to which the nonvolatile memory device 100 B is attached.

A memory controller 110 B of the nonvolatile memory device 100 B includes an access rate control part 106 B. Further, the access rate control part 106 B includes a status information generation part 113 . In the present embodiment, components other than the status information generation part 113 are the same as those of the first embodiment and are shown by the same numerals as those of the first embodiment.

On the other hand, the access device 200 B has a control part 203 and a cooling part 204 in addition to the display part 201 . The control part 203 controls an access to the nonvolatile memory device 100 B on the basis of status information given from the nonvolatile memory device 100 B, and drives the cooling part 204 . The cooling part 204 is, for example, an air-cooling device such as a fan or an electric cooling part such as a Peltier element, and cools the nonvolatile memory device 100 B.

Next, the status information generation part 113 in the access rate control part 106 B of the nonvolatile memory device 100 B will be explained. The status information generation part 113 generates the status information representing a status of the nonvolatile memory device, and transmits the generated information to the access device 200 B. The status information includes: the temperature T, a piece of warning information; a piece of access rate control execution information; a reading-writing allowable time tx; and a reading-writing allowable time Sx, and will be explained below. The status information generation part 113 includes: a ROM for a program to execute expressions (5-1) to (5-4) described below; and a computing unit, and calculates the reading-writing allowable time tx. The status information generation part 113 can include a table corresponding to expressions (5-1) to (5-4); and obtain the reading-writing allowable time tx by referring to the table. Further, the status information generation part 113 includes: a ROM for a program to execute expressions (6-1) and (6-2) described below; and a computing unit inside, and calculates the reading-writing allowable size Sx. The status information generation part 113 can include a table corresponding to expressions (6-1) and (6-2); and obtain the reading-writing allowable size Sx by referring to the table.

Then, the status information will be explained. The temperature T of the status information is a temperature of the nonvolatile memory device 100 B detected by the temperature detection part 111 .

The warning information is configured by, for example, 1-bit flag. This flag indicates whether the temperature T of the nonvolatile memory device 100 B is higher than the limit temperature Trisk or not.

The access rate control information is configured by, for example, 1-bit flag. This flag indicates whether or not the temperature-adaptive control part 112 presently controls an access rate.

The reading-writing allowable time tx is a time allowing the data reading and writing until the temperature T reaches the limit temperature Trisk. The reading-writing allowable time tx is calculated by the following expressions (5-1) to (5-4), where T is a temperature of the nonvolatile memory device 100 B, Rw is the access rate for the writing, Rr is the access rate for the reading, and t is the period of the accessing. TE is the environmental temperature of the nonvolatile memory device 100 B, and is 25° C. as a fixed value in the present embodiment.

In the Writing:

T=Fw ( Rw,t )+ TE   (5-1)

tx=Gw ( Rw,T,T risk)  (5-2).

In the Reading:

T=Fr ( Rr,t )+ TE   (5-3)

tx=Gr ( Rr,T,T risk)  (5-4).

Meanwhile, both of the access rates Rw and Rr are derived by: counting a time for incrementing the writing pointer WP or the reading pointer RP of the buffer 102 by using a counter and the like; and dividing 2 k bytes by the counted value (time). Fw and Fr are functions to uniquely calculate an average increased temperature ΔT of the nonvolatile memory device 100 B by using: the access rate Rw or Rr; and the time t. These functions can be derived as an approximate calculation expression based on a temperature experiment or a simulation in manufacturing the nonvolatile memory device 110 B, and has an integral characteristic shown in FIG. 8 of the first embodiment. Gw and Gr are functions to uniquely calculate times until the temperature T reaches the limit temperature Trisk, namely, the reading-writing allowable time tx, and can be obtained on the basis of Fw and Fr, respectively.

The reading-writing allowable size Sx is an allowable size of the data reading or writing until the temperature T reaches the limit temperature Trisk. The reading-writing allowable size Sx is calculated by the following expressions (6-1) and (6-2), where tx is the reading or writing allowable time obtained by expression (5-2) or (5-4).

In the Writing:

Sx=tx×Rw   (6-1).

In the Reading:

Sx=tx×Rr   (6-2).

In the nonvolatile memory system configured as described above, the data writing from the access device 200 B to the nonvolatile memory device 100 B will be subsequently explained. FIG. 13 is a time chart showing a data transmission and a data reception of the access device 200 B in writing data. The access device 200 B firstly transmits a writing command to the nonvolatile memory device 100 B. Next, the access device 200 B receives the status information ST from the nonvolatile memory device 100 B. The access device 200 B receives the status information ST and sequentially transfers 16 kbyte-data (a cluster unit) to the nonvolatile memory device 100 B. When the data transfer ends, the access device receives the status information from the nonvolatile memory device 100 B. The access device 200 B transfers file data to the nonvolatile memory device 100 B by alternately carrying out the transfer of 16-kB data and the reception of the status information in this manner. While receiving the busy information from the nonvolatile memory device 100 B, the access device 200 B interrupts the data transfer. When the transfer of file data ends after such process, the access device 200 B transmits a transfer end command to the nonvolatile memory device 100 B.

Next, a flow of the data writing will be explained. Since operations of the non access rate control mode and the access rate control mode at steps S 100 to S 109 are the same as those of the first embodiment, explanations thereof will be omitted. Newly-added step S 120 in the drawing will be explained below.

After step S 104 of FIG. 14 , the status information generation part 113 generates the status information and notifies the access device 200 B of the status information (S 120 ). The control part 203 of the access device 200 B makes the display part 201 display the notified status information, and drives the cooling part 204 on the basis of the status information to cool the nonvolatile memory device 100 B. This process will be explained in detail below.

When at least one of the above-mentioned status information has been notified to the access device 200 B, the access device 200 B carries out operations shown in the following (1) to (5) on the basis of the notified status information.

(1) When the status information generation part 113 notifies the access device 200 B of the temperature T as the status information, the control part 203 of the access device makes the display part 201 display the temperature T. The control part 203 has a ROM storing the limit temperatures Trisk and Tsafe inside. And, the control part compares the notified temperature T with the temperatures Trisk and Tsafe, drives the cooling part when the temperature is higher than Trisk, and stops the operation of the cooling part when the temperature is lower than Tsafe.

(2) When the status information generation part 113 notifies the access device 200 B of the warning information as the status information, the control part 203 of the access device displays the warning information on the display part 201 . In addition, when receiving the warning information, the control part 203 drives the cooling part 204 for a certain period.

(3) When the status information generation part 113 notifies the access device 200 B of the access rate control execution information as the status information, the control part 203 of the access device displays an execution status of access rate control on the display part 201 . In addition, after receiving the access rate control execution information, the control part 203 drives the cooling part 204 for a certain time when a present access rate is low.

(4) The status information generation part 113 generates the reading-writing allowable time tx as the status information, and notifies the access device 200 B of the time. In this case, the control part 203 of the access device displays the reading-writing allowable time tx on the display 201 . In addition, since having a ROM preliminarily storing a time (a threshold time) as a threshold, the control part 203 drives the cooling part 204 only for a certain time when the reading-writing allowable time tx is shorter than the threshold time. For example, in a case where the threshold time is one minute, when the reading-writing allowable time tx sent in each data transfer of one cluster becomes one minute or less, the cooling part 204 is driven. This threshold time is a time when the access device 200 B starts the driving of the cooling part 204 so that the temperature of the nonvolatile memory device 100 B cannot exceed Trisk.

(5) The status information generation part 113 generates the reading-writing allowable size Sx as the status information, and notifies the access device 200 B of the size. In this case, the control part 203 of the access device displays the reading-writing allowable size Sx on the display 201 . In addition, since having a ROM preliminarily storing a data size (a threshold size) as a threshold, the control part 203 drives the cooling part 204 only for a certain time when the reading-writing allowable size Sx is smaller than the threshold data size. For example, in a case where the threshold data size is 32 kB, when the reading-writing allowable size Sx sent in each data transfer of one cluster becomes 32 kB or less, the cooling part 204 is driven. This threshold size is a data size where the access device 200 B starts the driving of the cooling part 204 so that the temperature of the nonvolatile memory device 100 B cannot exceed Trisk.

Each type of the status information is used in the above-mentioned manner, and, the status information generation part 113 may generate only one of the above-mentioned five types of status information and notify the access device 200 B of the generated information, or may generate plural pieces of the status information and notify the access device 200 B of the generated information. A type of: the status information to be displayed on the display part 201 ; or the status information used for determining the driving of the cooling part 204 depends on a design or configuration of the access device 200 B, and accordingly can be variously changed.

Third Embodiment

FIG. 15 is a block diagram showing a nonvolatile memory system according to a third embodiment of the present invention. The nonvolatile memory system of the present embodiment is configured by including a nonvolatile memory device 100 C and the access device 200 A. A memory controller 110 C of the nonvolatile memory device 100 C includes a temperature calculation part 114 in an access rate control part 106 C. The temperature calculation part 114 does not use a sensor such as a thermistor but obtains the temperature T of the nonvolatile memory device 100 C in accordance with the approximate calculation based on expressions (5-1) or (5-3) explained in the second embodiment. In the present embodiment, the access device 200 A and the nonvolatile memory device 100 C are the same as those of the first embodiment except the temperature calculation part 114 , and are shown by the same numerals as those of the first embodiment. Additionally, in this approximate calculation, the environmental temperature TE at the time of starting the access is a fixed value, for example, 25° C. in the present embodiment.

The nonvolatile memory system according to the present embodiment is configured only by replacing the temperature detection part 111 of the first embodiment by the temperature calculation part 114 . Accordingly, the same operation as that of the nonvolatile memory system explained in the first embodiment can be carried out by using the temperature T calculated by the temperature calculation part 114 .

Also in this embodiment, the temperature-adaptive control part 112 may retain data of the limit temperature Trisk 2 as the third threshold temperature lower than the limit temperature Trisk. This temperature Trisk 2 indicates a temperature near a dangerous temperature for handling the nonvolatile memory device, and is a temperature higher than the safe temperature Tsafe. When the temperature T exceeds this limit temperature Trisk 2 , the temperature-adaptive control part 112 switches the data writing of the reading-writing control part 103 from a high-speed access to a low-speed access. And additionally, the temperature-adaptive control part 112 may transmit a switching command for the low-speed access to the access device 200 A to switch the data transfer of the access device 200 A from the high-speed access to the low-speed access.

In the present embodiment, since the temperature calculation part 114 calculates the temperature T in accordance with the approximate calculation, there is no need to mount a temperature sensor such as the thermistor on the nonvolatile memory device 100 C. Accordingly, this has an advantage in the downsizing of the nonvolatile memory device 100 C and a cost.

Fourth Embodiment

FIG. 16 is a block diagram showing a nonvolatile memory system according to a fourth embodiment of the present invention. The nonvolatile memory system according to the present embodiment is configured by including a nonvolatile memory device 100 D and an access device 200 D. A memory controller 110 D of the nonvolatile memory device 100 D includes a data size adaptive access rate control part 107 . The access device 200 D is configured by including the display part 201 and a control part 205 .

In the nonvolatile memory system of the present embodiment, only the access rate control part 107 and the control part 205 are different from the nonvolatile memory system of the first embodiment. Components other than these control parts are the same as those of the first embodiment, and are shown by the same numerals as those of the first embodiment.

The access rate control part 107 calculates an access rate at which a temperature of the nonvolatile memory device 100 D does not exceed the first threshold temperature Trisk in the access on the basis of a data size designated by the access device 200 D, and notifies the access device 200 D os the calculated access rate as access rate information (AR).

The control part 205 of the access device 200 D controls the access device 200 D including the display part 201 . Further, the control part 205 transmits to the nonvolatile memory device 100 D a size of data to be transmitted, and receives an access rate of data transfer from the nonvolatile memory device 100 D. Then, the access device 200 D accesses the nonvolatile memory device 100 D in accordance with the access rate, and transfers file data in units of 16 k bytes (a cluster unit).

The nonvolatile memory system configured as described above in the present embodiment will be explained. In the present embodiment, to simplify the description, only an operation of data writing will be explained and an explanation of data reading will be omitted.

FIG. 17 is a time chart showing the operation of data writing of the access device 200 D. In FIG. 17 , when the access device 200 D writes data to the nonvolatile memory device 100 D, the access device 200 D firstly transfers a writing command and a total size of data to be written (hereinafter referred to as a data size) to the nonvolatile memory device 100 D.

In FIG. 17 , the access device 200 D transfers data of 16 kbyte-unit one after another, pausing for a transfer pausing period. A period when the access device 200 D transfers 16 kbyte-data is represented as a transfer period Pa, and a time required for transferring 16 kbyte-data is represented as a transfer requirement time Pd. Meanwhile, the transfer requirement time Pd depends on a performance of the access device 200 D. The access device 200 D determines a ratio of the transfer period Pa to the transfer requirement time Pd on the basis of the access rate information notified from the nonvolatile memory device 100 D.

Next, a relation between the ration of the transfer period Pa to the transfer requirement time Pd and the access rate will be explained. When a bit width of an external bus connecting the access device 200 D to the host interface 101 is 4 bits and a transfer clock frequency of the access device 200 D is 240 MHz, the transfer requirement time Pd is approximately 133 μS in accordance with the following expression (7),

Pd= 16 kB/(240 MHz×0.5 B )≈133 μS  (7).

In addition, when the transfer period Pa is equal to the transfer requirement time Pd, that is, there is no transfer pausing period, the access rate Rw is 120 MB/S in accordance with the following expression (8),

Rw= 16 KB/ Pa= 16 KB/ Pd= 120 MB/S  (8).

When an access rate notified from the nonvolatile memory device 100 D is Rw and an access rate in the writing process of the access device 200 D under the condition of “Pa=Pd” is Rmax, the following expression (9) is satisfied,

PD/Pa=Rw/R max  (9).

The Rmax is 120 Mbytes/S at this time.

When Rw is 60 Mbytes/S in this expression (9), it can be obtained that Pd=Pa/2. In this case, the transfer period Pa is twice as long as the transfer requirement time Pd.

In addition, the control part 205 manages time required for the transfer requirement time Pd and the transfer period Pa by using a counter and the like in accordance with a ratio of the transfer period Pa to the transfer requirement time Pd, the ratio being determined on the basis of expression (9) and Rw, and controls a transfer start time of data for each 16 k bytes.

Next, using FIG. 18 , a writing control of the memory controller 110 D will be explained. In the initializing operation at power-on, the address management part 105 configures the logical-physical conversion table and the like in the address management part 105 on the basis of the logical block numbers and the physical management information recorded in the management regions of physical blocks in the flash memories 300 to 315 (S 200 ). In the following writing of data from the access device 200 D, the memory controller 110 D determines a physical address by using the logical-physical conversion table and the like. After that, the memory controller 110 D writes data temporarily retained in the buffer 102 to the flash memories 300 to 315 via the reading-writing control part 103 .

After the initializing process at S 200 , the memory controller 110 D waits for a writing command to order the data writing from the access device 200 D (S 201 ). When the memory controller 110 D has received the writing command from the access device 200 D, the CPU 104 passes a logical address transferred as an argument of the writing command to the address management part 105 . The address management part 105 determines a physical block on the basis of the logical address.

Moreover, the CPU 104 transfers a data size transferred following the writing command to the access rate control part 107 . The access rate control part 107 determines an access rate on the basis of: the transferred data size; and expressions (10-1) or (10-2) (S 202 ), where Rw is the access rate for the writing, Rr is the access rate for the reading, and Ds is the data size.

In the Writing:

Rw=Hw ( Ds )  (10-1).

In the Reading:

Rr=Hr ( Ds )  (10-2).

Meanwhile, Hw and Hr are functions to uniquely derive values at which the access rates Rw and Rr become the highest by employing the data size Ds as a variable within a range where the temperature T of the nonvolatile memory device 100 D does not exceed the limit temperature Trisk of the first threshold temperature. These functions can be derived as approximate calculation expressions based on a temperature experiment and a simulation in manufacturing the nonvolatile memory device 100 D. Meanwhile, when tables corresponding to expressions (10-1) and (10-2) are included in the access rate control part 107 , the access rates Rw and Rr may be obtained by referring the tables.

The access rate control part 107 informs the access device 200 D of the access rate Rw calculated in this manner (S 203 ).

The access device 200 D determines the ratio of the transfer period Pa to the transfer requirement time Pd on the basis of the notified access rate. The access device 200 D transfers data to the nonvolatile memory device 100 D in units of 16 kbyte-data in accordance with this ratio. The data is temporarily retained in the buffer 102 from a region indicated by the writing pointer WP (S 204 ). At the time when the 2 kbyte-data is retained in the buffer 102 , the reading-writing control part 103 reads the data retained in the buffer 102 from the buffer 102 in accordance with the reading pointer RP, and writes the read data to the nonvolatile memory 120 (S 205 ). Such processes at S 204 and S 205 are repeated until 16 kbyte-data have been completely transferred from the access device 200 D (S 206 ). Meanwhile, timings of the data transfer and the writing are the same as those of the first embodiment.

After that, it is judged whether or not the CPU 104 has received a transfer end command from the access device 200 D (S 207 ). When the CPU has received the transfer end command, the flow proceeds to S 201 and the CPU waits for next reading or writing commands. On the other hand, when the CPU 104 has not received the transfer end command from the access device 200 D, the flow proceeds to S 204 and the data is temporarily retained in the buffer 102 subsequently.

As described above, in the nonvolatile memory system shown in the fourth embodiment, the access rate control part 107 determines an access rate on the basis of a data size designated by the access device 200 D. The access rate control part 107 notifies the access device 200 D of this access rate, and the access device 200 D writes data in accordance with the access rate. Thus, the data can be written at the highest access rate within a range where the temperature T does not exceed the limit temperature Trisk. That is, a burn of user caused by the temperature increase of the nonvolatile memory device 100 D can be avoided and the data can be written at a high speed.

In the present embodiment, the access rate is controlled by controlling the ratio of the transfer period Pa to the transfer requirement time Pd, however, the access rate may be controlled by controlling the transfer requirement time Pd. In addition, the data transfer is not limited to 16 kB-transfer and may be carried out in arbitrary units.

Fifth Embodiment

FIG. 19 is a block diagram showing a nonvolatile memory system according to a fifth embodiment of the present invention. As shown in FIG. 19 , the nonvolatile memory system according to the present embodiment is configured by including a nonvolatile memory device 100 E and an access device 200 E to which the nonvolatile memory device 100 E is attached. In the nonvolatile memory system according to the present embodiment, the access device 200 E is newly provided with a temperature output part 206 . The temperature output part 206 arranges a temperature sensor in the close vicinity of the nonvolatile memory device 100 E, and supplies temperature information of the nonvolatile memory device 100 E detected by the temperature sensor to the nonvolatile memory device 100 E via the control part 202 and an external bus. A timing to output the temperature information is periodical during reading and writing commands execution.

Meanwhile, the memory controller 110 E of the nonvolatile memory device 100 E includes a temperature retention part 115 in an access rate control part 106 E. The temperature retention part 115 does not use a sensor such as a thermistor but receives the temperature information from the access device 200 E and retains the information as the temperature T of the nonvolatile memory device 100 A. In the present embodiment, components other than the temperature retention part 115 and the temperature output part 206 included in the access device 200 E are the same as those of the first embodiment, and are shown by the same numerals as those of the first embodiment. The nonvolatile memory device 100 E receives via the host interface 101 the temperature information supplied from the access device 200 E.

As described above, in the nonvolatile memory system in the present embodiment, the temperature detection part 111 is replaced by the temperature retention part 115 , and since the temperature retention part 115 treats the temperature information received from the access device 200 E as the temperature T of the nonvolatile memory device 100 E, the same operation as that of the nonvolatile memory system explained in the first embodiment can be carried out.

That is, when the temperature T of the nonvolatile memory device 100 E exceeds the limit temperature Trisk, the temperature-adaptive control part 112 interrupts the writing operation of the reading-writing control part 103 , and transfers busy information to the access device 200 E to make the access device 200 E interrupt the data transfer. In addition, when the temperature T falls below the safe temperature Tsafe, the nonvolatile memory device 100 E resumes the data writing and the data transfer. The access rate can be suppressed in this manner, thereby a burn of user caused by temperature increase of the nonvolatile memory device 100 E can be avoided even in the high-speed data writing.

The access device 200 E can be various types of devices, for example, a low power consumption device such as an audio player that works by a small rechargeable battery or a dry-cell battery, a high power consumption device such as a movie camera (a camcorder) that has a large-capacity rechargeable battery and records a moving image and a sound, and home-use video recorder, television, and personal computer working by an AC power supply. Among them, a device which consumes a large amount of power and the internal temperature becomes high originally includes a temperature sensor in many cases. In a case where a temperature sensor such as a thermistor in the access device 200 E is attached: to an installation position of the nonvolatile memory device, for example, a slot of memory card; or in the vicinity of the position, there is sometimes a case where the temperature information supplied from the access device 200 E to the nonvolatile memory device 100 E may be used as the temperature T of the nonvolatile memory device 100 E. In this case, the originally included temperature sensor may used as a temperature sensor of the temperature output part 206 . In this manner, there is no need to mount a temperature sensor such as a thermistor on the nonvolatile memory device 100 E, resulting in advantages in downsizing of the nonvolatile memory device 100 E and in a cost.

Meanwhile, the temperature-adaptive control part 112 may retain data of the limit temperature Trisk 2 as the third threshold temperature lower than the limit temperature Trisk. When the temperature T exceeds this limit temperature Trisk 2 , the temperature-adaptive control part 112 switches the data writing of the reading-writing control part 103 from the high-speed access to the low-speed access. And additionally, the temperature-adaptive control part 112 may transmit a switching command for the low-speed access to the access device 200 A to switch the data transfer of the access device 200 A from the high-speed access to the low-speed access.

In addition, the limit temperature Trisk and the safe temperature Tsafe are determined on the basis of the quality standard used for manufacturing the nonvolatile memory device 100 E, and thus can take various values.

Sixth Embodiment

In the above-described first and third embodiments, the environmental temperatures TE of the nonvolatile memory devices 100 A and 100 C was fixed values, however, various types of devices accepting the nonvolatile memory device can be actually assumed. Accordingly, an environmental temperature of the nonvolatile memory device widely varies depending on a type of the access device.

In a low power consumption access device such as an audio player working by a small rechargeable battery or a dry-cell battery, a temperature increase of the device itself is substantially small. When a power consumption of the access device is low, the temperature increase is sometimes a few degrees from an external temperature. In such a case, the access device can treat the environmental temperature TE of the nonvolatile memory device as a fixed value, 25° C. as explained in the first embodiment without a practical problem.

On the other hand, there is an access device of a high power consumption such as a movie camera (a camcorder) that has a large-capacity rechargeable battery and records a moving image and a sound, and further home-use video recorder, television, and personal computer working by an AC power supply. Among them, some access devices generate heat of 30° C. to 60° C. by itself and raise its internal temperature to approximately 60° C. Accordingly, when the temperature T of the nonvolatile memory device is calculated by using a fixed value of 25° C. as the environmental temperature TE of the nonvolatile memory device, the temperature differs substantially-wide from an actual temperature of the nonvolatile memory device. Accordingly, since a desired access control cannot be realized, the nonvolatile memory device becomes very hot and may cause a risk of a burn.

In the case where the temperature T (≈the environmental temperature TE) at a writing start time is assumed to be 25° C. as explained in the first embodiment, after that, the temperature T gradually reaches 85° C. in an asymptotic manner due to the data writing as shown in FIG. 8 . However, in a case where the temperature T (≈the environmental temperature TE) at a writing start time was actually 40° C., the temperature T gradually reaches around 100° C. of the saturate temperature in an asymptotic manner due to the data writing as shown in FIG. 20 when the writing is carried out by a high-speed access under the condition explained in the first embodiment.

As described above, in the case where the amount of power consumption and the heating value of the access device itself is large, the temperature T of the nonvolatile memory device 100 A calculated by employing the environmental temperature TE as a fixed value differs from the temperature T of the nonvolatile memory device 100 A under an actual use environment.

FIG. 21 is a block diagram showing the nonvolatile memory system according to the sixth embodiment of the present invention. As shown in FIG. 12 , the nonvolatile memory system according to the present embodiment is configured by including a nonvolatile memory device 100 F and an access device 200 F to which the nonvolatile memory device 100 F is attached. In the present embodiment, components other than: a temperature calculation part 116 of the nonvolatile memory device 100 F; and an environmental temperature output part 207 A included in the access device 200 F are the same as those of the first embodiment, and are shown by the same numerals as those of the first embodiment. The environmental temperature output part 207 A has a temperature sensor such as a thermistor, and measures and outputs the environmental temperature TE of the nonvolatile memory device 100 F. A memory controller 110 F of the nonvolatile memory device 100 F includes the temperature calculation part 116 in an access rate control part 106 F. The temperature calculation part 116 does not use a sensor such as a thermistor but obtains the temperature T of the nonvolatile memory device 100 F in accordance with the approximate calculation based on expressions (5-1) or (5-3) explained in the second embodiment.

T=Fw ( Rw,t )+ TE   (5-1)

T=Fr ( Rr,t )+ TE   (5-3),

where T is the temperature of the nonvolatile memory device 100 F, Rw is the access rate for the writing, Rr is the access rate for the reading, and t is the period of the accessing.

Both of the access rates Rw and Rr are derived by: counting a time for incrementing the writing pointer WP or the reading pointer RP of the buffer 102 by using a counter and the like; and dividing 2 k bytes by the counted value (time). Fw and Fr are functions to uniquely calculate an average increased temperature ΔT of the nonvolatile memory device 100 F by using: the access rate Rw or Rr; and the time t. These functions can be derived as an approximate calculation expression based on a temperature experiment and a simulation in manufacturing the nonvolatile memory device 100 F, and has an integral characteristic shown in FIG. 8 and FIG. 20 .

In the present embodiment, the access device 200 F detects the environmental temperature TE of the nonvolatile memory device 100 F by using the environmental temperature output part 207 A, and supplies the detected temperature to the nonvolatile memory device 100 F via the control part 202 and the external bus.

The nonvolatile memory device 100 F receives temperature information supplied from the access device 200 F via the host interface 101 . The temperature calculation part 116 of the access rate control part 106 F employs the temperature information as the environmental temperature TE in the calculation of expressions (5-1) and (5-3).

FIG. 22 is a graph showing a temporal characteristic of the temperature T in the case where the writing process is carried out in the access rate control mode as shown in FIG. 10 by: interrupting the data transfer at the time tr; and then resuming the data transfer at the time is in the high-speed access. In FIG. 22 , the temperature T at a writing start time is a value of the environmental temperature TE supplied from the environmental temperature output part 207 A of the access device 200 F.

After that, the temperature T gradually approaches the saturate temperature in an asymptotic manner due to an electric power consumption of the data writing. However, the access device 200 F interrupts the data transfer at the time tr when the temperature T exceeds the limit temperature Trisk, and the nonvolatile memory device 100 F interrupts the data writing carried out by the reading-writing control part 103 . The temperature T accordingly starts to fall, and the access device 200 F resumes data transfer and the reading-writing control part 103 resumes the writing at the time is when the temperature T has fallen below the safe temperature Tsafe, thereby the temperature begins to increase again.

Meanwhile, the above-mentioned explanation is a description after the temperature in the access device 200 F has reached a static state. However, the environmental temperature TE of the nonvolatile memory device is not a constant temperature at the starting of operation, and the temperature increases with the operation of the access device 200 F. Accordingly, as shown in FIG. 23 , a temperature change of the nonvolatile memory device 100 F at the high-speed access is shown as a curved line formed by adding the environmental temperature TE represented by a two-dot chain line, namely, a temperature in the access device to an increased temperature ΔT of the nonvolatile memory device 100 F, and a more-accurate temperature of the nonvolatile memory device 100 F can be derived. Thus, when the access rate control is carried out at the timing, for example, the high-speed access, a temperature change of the nonvolatile memory device 100 F tracks as represented by a solid line of FIG. 24 a curved line formed by adding the environmental temperature represented by a two-dot chain line like in FIG. 22 , namely, a temperature in the access device to an increased temperature ΔT of the nonvolatile memory device 100 F, and thus the temperature of the nonvolatile memory device 100 F can be controlled more accurately.

As described above, according to the sixth embodiment, since the temperature T of the nonvolatile memory device 100 F is calculated under conditions: the environmental temperature of the nonvolatile memory device 100 F is not a fixed value, for example, 25° C.; the access device 200 F supplies a temperature in the device in the operation to the nonvolatile memory device 100 F; and this temperature is treated as the environmental temperature TE of the nonvolatile memory device 100 F, the more-accurate temperature T can be calculated.

Modified Example

Next, a modified example of the sixth embodiment will be explained. In the modified example, an environmental temperature output part 207 B is included in place of the environmental temperature output part 207 A. The environmental temperature output part 207 B preliminarily retains information regarding a temperature increase in the access device 200 F, for example, at factory shipment, and supplies the information to the nonvolatile memory device 100 F.

The access device 200 F differs in a power consumption and its volume, and an internal temperature varies because of these factors. Accordingly, the environmental temperature output part 207 B retains a saturate value of the temperature TE that indicates a degree of temperature increasing when the access device 200 F actually operates, for example, in a nonvolatile memory such as a ROM (Read Only Memory), a flash memory or a hard wired logic for each type of device. Then, the temperature information retained in this manner is supplied at the time of access. The nonvolatile memory device 100 F controls the access by directly assigning the given temperature TE to expressions (5-1) or (5-3). In this case, a similar process can be carried out without using a temperature sensor in the access device.

Seventh Embodiment

Next, a seventh embodiment will be explained. FIG. 25 is a block diagram showing a nonvolatile memory system according to the seventh embodiment of the present invention. As shown in FIG. 25 , the nonvolatile memory system according to the present embodiment is configured by including a nonvolatile memory device 1000 and an access device 200 G to which the nonvolatile memory device 1000 is attached. In this embodiment, the access device 200 G commands the nonvolatile memory device 1000 to treat the temperature as: the temperature T of the nonvolatile memory device 1000 ; or the environmental temperature TE of the nonvolatile memory device 100 G on the basis of a position of a temperature sensor such as a thermistor attached in the access device 200 G.

In the case where the temperature sensor such as a thermistor in the access device 200 G is attached: to an installation position of the nonvolatile memory device (for example, a slot of memory card); or in the vicinity of the position, a temperature information output part 208 sets a flag to indicate that the temperature information supplied from the access device 200 G to the nonvolatile memory device 1000 has to be treated as the temperature T of the nonvolatile memory device 1000 and outputs the flag with the temperature information. On the other hand, in the case where the temperature sensor is attached to a position away from the installation position of the nonvolatile memory device, the temperature information output part 208 sets a flag to indicate that the temperature information supplied from the access device 200 G to the nonvolatile memory device 1000 has to be treated as the environmental temperature TE of the nonvolatile memory device 1000 and outputs the flag with the temperature information.

FIG. 26A shows the temperature information supplied from the access device to the nonvolatile memory device 100 G, and FIG. 26B shows an example of data structure of the flag. Here, a data region of 1 byte is allocated for the temperature information. However, the temperature information may be represented in less than 1 byte in order to reduce a circuit (for example, a register), or contrary may be represented by bits more than 1 byte allocated in order to handle an extensive temperature range.

Additionally, the flag is composed of: an R flag configured by 1 bit; and S flag configured by 2 bits.

Next, a state of each flag and its operation in FIG. 27 will be explained. At first, when S0 and S1 of the S flag are 0 and the R flag is 0, namely, in a case of a status A, the flag indicates that information regarding a degree of temperature increase of the access device 200 G at an operation is not stored.

Meanwhile, in a case of a status B of FIG. 27 , namely, when the R flag is 1, the flag indicates that a saturate value of the temperature TE indicating a degree of temperature increase of the access device 200 G at an operation is stored in the access device 200 G. In this case, as in the above-mentioned modified example, the saturation value of TE is transferred to the nonvolatile memory device 100 G, and a temperature is calculated by employing this temperature as TE.

Next, in a case of a status C, namely, when S0 bit of the S flag is 1 and the R flag is 0, the case shows that a temperature sensor such as a thermistor is incorporated in the access device 200 A, and the sensor is attached to a position away from the installation position of the nonvolatile memory device, thereby orders to treat supplied temperature information as the environmental temperature TE of the nonvolatile memory device 100 G.

In this case, as explained in the above-described sixth embodiment, the nonvolatile memory device 1000 receives the temperature information supplied from the access device 200 G via the host interface 101 . Then, the temperature detection part 117 of the access rate control part 106 G employs this temperature as the environmental temperature TE of the nonvolatile memory device 100 G. The temperature T of the nonvolatile memory device 1000 is obtained by an approximate calculation based on expressions (5-1) or (5-3) explained in the second embodiment. The subsequent operation is the same as that of the sixth embodiment.

In a case of a status D of FIG. 27 , namely, when S1 bit of the S flag is 1 and the R flag is 0, the case shows that a temperature sensor such as a thermistor is incorporated in the access device 200 G, the temperature sensor is attached: to the installation position of the nonvolatile memory device; or in the vicinity of the position, thereby orders to treat supplied temperature information as the temperature T of the nonvolatile memory device 1000 because.

In this case, as explained in the fifth embodiment, the nonvolatile memory device 1000 receives the temperature information supplied from the access device 200 G via the host interface 101 . The temperature detection part 117 of the access rate control part 106 G employs this temperature as the temperature T of the nonvolatile memory device 100 G. The subsequent operation is the same as that of the fifth embodiment.

Meanwhile, the flag may be represented in less than 3 bits in order to reduce a circuit (for example, a register), and contrary may be represented by bits more than 3 bits allocated in order to: transfer other information together; and separately represent information regarding the temperature sensor.

Eighth Embodiment

FIG. 28 is a block diagram showing a nonvolatile memory system according to an eighth embodiment of the present invention. As shown in FIG. 28 , the nonvolatile memory system according to the embodiment is configured by including an access device 200 H and a nonvolatile memory device 100 H.

[Access Device]

The access device 200 H includes a system control part 211 , a codec part 212 , a ROM/RAM 213 , a display part 214 , a display control part 215 , and a nonvolatile memory device control part 216 .

The system control part 211 controls the whole of the access device 200 H, and the codec part 212 generates compression data of moving image. The ROM/RAM 213 stores program used for an operation of the system control part 211 , and is further used as a work region. The display part 214 displays information regarding the nonvolatile memory system, and the display control part 215 controls a display to the display part 214 . The nonvolatile memory device control part 216 H accesses the nonvolatile memory device 100 H, and includes a memory device access part 221 , a temperature detection part 222 , an access rate control part 223 , and a temperature parameter retention part 224 .

The memory device access part 221 reads and writes data from and to the nonvolatile memory device 100 H via an external bus. The temperature detection part 222 includes a temperature sensor, and detects the temperature T of the nonvolatile memory device 100 H. The access rate control part 223 controls an access rate at data-writing and data-reading to the nonvolatile memory device 100 H on the basis of a temperature parameter. The temperature parameter retention part 224 retains the temperature parameter explained below in place of the temperature parameter of the nonvolatile memory device 100 H.

In FIG. 28 , components which are not essential for the access device 200 H of the present invention, for example, other external input-output terminals for image and audio and various types of connectors are not shown.

[Nonvolatile Memory Device]

The nonvolatile memory device 100 H includes at least one nonvolatile memory 120 and a memory controller 110 H.

The nonvolatile memory 120 retains user data in the same manner as that of the first embodiment, and a flash memory is employed for example. The memory controller 110 H reads and writes data from and to the nonvolatile memory 120 on the basis of requirements of data-reading and data writing from the access device 200 H.

The memory controller 110 H includes the CPU 104 , a register part 108 , the host IF 101 , the buffer 102 , and the reading-writing control part 103 .

The CPU 104 controls the whole of the memory controller 110 H. The register part 108 retains control information of the nonvolatile memory device 100 H such as the temperature parameter described below. The host IF 101 is an interface for transmitting and receiving data to and from the access device 200 H via an external bus. Meanwhile, the external bus is configured by including a bus for clock and a bus for command and data. The buffer 102 temporarily retains transmitted and received data to and from the access device 200 H. The reading-writing control part 103 reads and writes data from and to the nonvolatile memory 120 via a memory bus.

The address management part 105 is a block for: converting a logical address transferred in accordance with an access of the access device 200 A into a physical address of the nonvolatile memory 120 ; and managing, for example, a recording state of the nonvolatile memory 120 . Meanwhile, since an address management method can be realized by using a common technique, an explanation thereof is omitted.

FIG. 29 shows the temperature parameter retained by the register part 108 of the memory controller 110 H. The temperature parameter shown in FIG. 29 includes an operable maximum temperature Tmax, a temperature increasing speed Tu, a saturate temperature Ts, and a temperature decreasing speed Td.

The operable maximum temperature Tmax is the maximum temperature allowed in an access to the nonvolatile memory device 100 H. The temperature increasing speed Tu is a speed of temperature increase of the nonvolatile memory device 100 H of a case where an access is carried out at a certain rate, and the saturate temperature Ts is a temperature to which the increasing temperature converges. The temperature decreasing speed Td is a speed of temperature fall of the nonvolatile memory device 100 H of a case where a data transfer is not carried out.

The temperature parameter retains the temperature increasing speeds Tu and the saturate temperatures Ts for a plurality of access rates, and in FIG. 29 , N kinds of the temperature increasing speeds Tu 1 to Tun and N kinds of saturate temperatures Ts 1 to Tsn are retained corresponding to N kinds of access rates.

Meanwhile, the temperature parameter retention part 224 of the access device 200 H preliminarily stores the above-mentioned temperature parameter for each type of the nonvolatile memory device. Accordingly, when the nonvolatile memory device does not retain the temperature parameter, this parameter can be used in place of the temperature parameter of the nonvolatile memory device.

[Access Rate Control Method]

Using FIG. 30 and FIG. 31 , a method to control an access rate by the access device 200 H will be explained. The command and data are transferred in synchronization with a rising edge of clock and in predetermined units. For example, the command is transferred in units of 4 bytes, and the data is transferred in units of 512 bytes. A start flag, an end flag, a CRC code for detecting an error may be added to the command and data.

At first, a first access rate control method will be explained. In this method, the access device 200 H changes a clock frequency to control an access rate. FIG. 30 shows three different relationships between a waveform of clock bus and transferred command and data in this method. In the three cases (A) to (C) of FIG. 30 , since a clock period of the case (A) is the shortest, a clock frequency of the case (A) is the highest. Since the clock periods become longer in the order from the case (B) to the case (C), the clock frequencies also become lower in the order from the case (B) to the case (C). As shown in the drawing, a transfer period of command and data transferred in synchronization with the clock will vary depending on the difference of the clock frequency. Since the transfer periods of command and data transferred in synchronization with the clock become shorter in the case where the clock frequency is high, the case (A) shows that an access rate is higher than those of the cases (B) and (C) and thus an access is carried out at a higher-speed. The access rate can be controlled by changing the clock frequency in this manner.

Next, a second access rate control method will be explained. In this method, the access device 200 H controls an access rate by changing transfer intervals of command and data of a predetermined unit. FIG. 31 shows relationships between a waveform of clock bus and transferred command and data in this method. Though clock frequencies in the cases (A) to (C) are identical, the transfer interval of 512-byte data varies. The transfer interval of the case (A) is the shortest, and becomes longer in the order from the case (B) to the case (C). The shorter the transfer interval is, the shorter a period of transferring data in a predetermined unit is, and thus, in the case (A), the access rate is the highest and an access is carried out at the highest-speed. On the other hand, in the cases (B) and (C), since the transfer of command and data of a predetermined unit is carried out at constant intervals, a lower-speed access is carried out in comparison with the case (A). The access rate can be controlled by changing the interval of data transfer in this manner.

Meanwhile, of the two access rate control methods explained in FIG. 30 and FIG. 31 , only either one of them may be applied to the access device 200 H or a combination of them may be applied to the access device. When these two control methods are combined to change the clock frequency and the transfer interval of command and data, the access rate can be changed more variously than the case of using only one of the control methods.

[Set of Access Rate]

Next, a first access rate setting method will be explained. FIG. 32 shows a relationship between a temperature of the nonvolatile memory device 100 H and a time in a graph for each access rate, the relationship being of a case where the access device 200 H of the present embodiment accesses the nonvolatile memory device 100 H. In FIG. 32 , an initialization temperature Tini is the temperature T of the nonvolatile memory device 100 H that is detected by the access device 200 H when the writing has started. The maximum temperature Tmax is the highest temperature at which the nonvolatile memory device 100 H can operate, the temperature is included in the temperature parameter read from the register part 108 of the nonvolatile memory device 100 H. In addition, the limit temperature Trisk is an upper limit of a temperature at which a user is not at risk of a burn when handling the nonvolatile memory device 100 H. The temperature depends on a specification of the access device 200 H. Curved lines ( 1 ), ( 2 ), and ( 3 ) in the drawing show temperature increase at different access rates, respectively, and the curved line ( 1 ) shows a case of the highest access rate. The saturate temperatures at the respective access rates are shown by Ts 1 , Ts 2 , and Ts 3 , respectively.

Since the temperature parameter retained by the nonvolatile memory device 100 H is under a condition different from a unique condition that the access device 200 H has, the access device 200 H calculates the curved lines ( 1 ) to ( 3 ) which are correspondence relationships between data reading and writing time and a temperature by using a function on the basis of: the temperature parameter of the register part 108 ; and the unique condition of the access device 200 H. This unique condition of the access device 200 H includes a condition related to temperature increase of the nonvolatile memory device 100 H, for example, dimensions and materials of the case of the access device 200 H and a shape of a connector part for connecting to the nonvolatile memory device 100 H. In addition, the function to calculate each of the curved lines ( 1 ) to ( 3 ) is preliminarily derived by a temperature experiment or a simulation in manufacturing the access device 200 H. Further in FIG. 32 , the curved lines ( 1 ) to ( 3 ) corresponding to three access rates have been explained as examples, however, the curved line derived by the access device 200 H is not limited to the three curved lines. The access device 200 H derives curved lines representing temperature increase regarding all access rates corresponding to the temperature parameter among access rates with which the access device 200 H is provided. Or, the access device 200 H may start the derivation from a lower rate of the provided access rates and may finish at the time when the calculated saturate temperature exceeds the limit temperature Trisk.

A curved line whose saturate temperature does not exceed the limit temperature Trisk and that is closest to the limit temperature Trisk is selected from among the curved lines obtained in this manner. Then, the access rate corresponding to the temperature parameter used in deriving the curved line is determined as an access rate for the nonvolatile memory device 100 H. For example, in the case of FIG. 32 , when the access device 200 H selects the curved line ( 3 ), the saturate temperature Ts 3 does not exceed the limit temperature Trisk. Accordingly, the access device 200 H carries out an access by selecting the access rate corresponding to the curved line ( 3 ).

Next, a second access rate setting method will be explained. In a case where the access device 200 H finishes the data transfer in short time, the access device 200 H can select an access rate at which the saturate temperature exceeds the limit temperature Trisk. Specifically, even in a case where the data transfer is carried out at an access rate at which the saturate temperature exceeds the limit temperature Trisk, there is no problem if the data transfer finishes before the environmental temperature of the nonvolatile memory device 100 H reaches the limit temperature Trisk.

For example, in FIG. 32 , even in a case where an access rate corresponding to the curved line ( 1 ), when time required for the data transfer, namely, time for continuously accessing the nonvolatile memory device 100 H is time to or less, the environmental temperature of the nonvolatile memory device 100 H does not exceed the limit temperature Trisk. Then, the access device 200 H selects the access rate corresponding to the curved line ( 1 ). In the similar manner, when time for the continuous accessing is time tb or less, the access device 200 H selects the access rate corresponding to the curved line ( 2 ). The time required for the data transfer is calculated on the basis of a size of transferred data and the access rate. In this manner, when a possible high-speed access rate is selected within a range where the environmental temperature of the nonvolatile memory device 100 H does not exceed the limit temperature Trisk in consideration of the time for continuously accessing the nonvolatile memory device 100 H, the data transfer finishes in short time. In addition, since the access device 200 H includes the display part 214 , the access device 200 H can display the selected access rate and the temperature parameter.

[Access Procedure]

FIG. 33 is a flowchart showing a control of a case where the access device 200 H according to the present embodiment accesses the nonvolatile memory device 100 H. In FIG. 33 , the access device 200 H firstly initializes the nonvolatile memory device 100 H (S 300 ), and sets the nonvolatile memory device 100 H readable and writable. When a reading command or a writing command to the nonvolatile memory device 100 H is issued (S 301 ), the temperature detection part 222 detects the temperature T of the nonvolatile memory device 100 H by using the temperature sensor (S 302 ). Next, the access device 200 H judges whether or not the nonvolatile memory device 100 H retains a temperature parameter (S 303 ). When retaining a temperature parameter, the nonvolatile memory device 100 H obtains the temperature parameter and calculates a saturate temperature of the nonvolatile memory device 100 H based on the parameter (S 304 ). If the nonvolatile memory device 100 H does not retain a temperature parameter, the access device 200 H calculates a saturate temperature of the nonvolatile memory device 100 H by using a temperature parameter retained by the temperature parameter retention part 224 (S 305 ). After S 304 or S 305 , the access rate control part 223 of the access device 200 H determines an access rate on the basis of these calculation results in the above-mentioned manner and sets the access rate for data reading and writing (S 306 ).

After that, the memory device access part 221 reads or writes data from or to the nonvolatile memory device 100 H at the set access rate (S 307 ). When a process at S 307 starts, the temperature detection part 222 detects the temperature T of the nonvolatile memory device 100 H, and the memory device access part 221 compares this temperature T with the limit temperature Trisk of the first threshold temperature (S 308 ). When the temperature T is lower than the limit temperature Trisk at S 306 , it is confirmed whether or not the reading or writing of data ends (S 309 ). When the reading or writing of data have not ended, the process returns to S 307 and the access part continues the reading or writing of data. When the reading or writing of data has ended, the process returns to S 301 and the memory device waits for a next reading command or writing command. In the process at S 308 , when the temperature T is higher than the limit temperature Trisk, the access part stops the reading or writing of data and waits until the temperature T falls below the temperature Trisk. When the temperature T has fallen below the limit temperature Trisk, the access part resumes the reading or writing of data and the process proceeds to S 309 . Meanwhile, since the access rate is determined to be the limit temperature Trisk or less, the temperature T usually never exceeds the temperature Trisk at S 308 . In this manner, an access to the nonvolatile memory device 100 H is carried out.

As explained above, in the nonvolatile memory system of the present embodiment, the access device 200 H selects an access rate by using the temperature parameter of the nonvolatile memory device 100 H, and reads and writes data. Accordingly, the nonvolatile memory device, the access device, and the nonvolatile memory system which eliminate a risk of a burn when a user handles the nonvolatile memory device 100 H and which can read and write data at a high speed.

Ninth Embodiment

FIG. 34 is a block diagram showing a nonvolatile memory system according to a ninth embodiment of the present invention. As shown in FIG. 34 , the nonvolatile memory system of the present embodiment is configured by including an access device 200 I and the nonvolatile memory device 100 H. The access device 200 I has a nonvolatile memory device control part 216 I. The access rate control part 225 controls an access rate of data reading or writing to the nonvolatile memory device 100 H. Meanwhile, in FIG. 34 , the same numerals as those of FIG. 28 are added to the same components as those of the eighth embodiment.

FIG. 35 is a flowchart showing a control flow of a case where the access device 200 I accesses the nonvolatile memory device 100 H. In FIG. 35 , S 300 to S 305 and S 309 are the same processes as those of S 300 to S 305 and S 309 in FIG. 32 of the eighth embodiment, and thus an explanation thereof will be omitted.

In FIG. 35 , following S 304 or S 305 , the access rate control part 225 sets an access rate coinciding with that of the access rate 200 I or the maximum accessible access rate of the access device 200 I as an access rate to the nonvolatile memory device 100 H (S 400 ). Subsequently, the access rate control part 225 sets a transmittable time trw described later by using: the temperature T obtained at S 302 ; the saturate temperature obtained at S 340 ; and the access rate set at S 400 . After this, during the transmittable time trw, the memory device access part 221 reads data or writes data from or to the nonvolatile memory device 100 H at the set access rate (S 402 ). The temperature detection part 222 detects the temperature T of the nonvolatile memory device 100 H and compares the temperature with the limit temperature Trisk, or measures a transfer time t required for continuously accessing the nonvolatile memory device 100 H and compares the transfer time t with the transmittable time trw allowing a continuous access to the nonvolatile memory device 100 H (S 403 ). When the temperature T of the nonvolatile memory device 100 H is lower than the predetermined limit temperature Trisk or when the transfer time t is shorter than the transmittable time trw, the process proceeds to S 309 and it is judged whether or not a transfer end command has been issued. When the temperature T of the nonvolatile memory device 100 H is the predetermined limit temperature Trisk or more or when the transfer time t is the transmittable time trw or more, the access part interrupts the reading or writing of data and stands by until the temperature falls to or below the temperature Tsafe of the second threshold temperature (S 404 ). When the temperature has fallen to or below the safe temperature Tsafe, the access part resumes the reading or writing of data, and the process proceeds to S 309 . When the reading or writing has not finished at S 309 , the process returns to S 402 , and the transmitting of command and the reading or writing of data are continued. When the reading or writing of data have finished, the flow of process returns to S 301 and the memory device waits for a next reading command or writing command.

FIG. 36 shows a relationship between the environmental temperature T of the nonvolatile memory device 100 H and time in each access rate, the relationship being of a case where the access device 200 I of the present embodiment accesses the nonvolatile memory device 100 H. In FIG. 36 , the initial temperature Tini and the limit temperature trisk are the same as those explained in the eighth embodiment. The safe temperature Tsafe is the second threshold temperature that is lower than the limit temperature trisk and is determined on the basis of specifications of the access device 200 H. The safe temperature Tsafe is a criterion used for determining whether or not the data transfer is resumed after the environmental temperature of the nonvolatile memory device 100 H increases to the limit temperature Trisk once and the data transfer is interrupted.

The wavy curved lines ( 1 ), ( 2 ), and ( 3 ) showing correspondence relationships between time of data reading and writing and temperature in FIG. 36 , show cases each at different access rate. Similar to the eighth embodiment, a temperature increase shown by each curved line is calculated by using a function derived from a temperature experiment or a simulation on the basis of: the temperature increasing speed Tu corresponding to each access rate in FIG. 29 and a unique condition of the access device 200 I. In addition, a temperature fall at stopping the transfer is calculated on the basis of: the temperature decreasing speed Td in FIG. 29 and the unique condition of the access device 200 I. At first, a curved line reaching from the initial temperature Tini to the limit temperature Trisk is created by using the temperature increasing speed Tu, and then a curved line from the limit temperature Trisk to the safe temperature Tsafe is created by using the temperature decreasing speed Td. Subsequently, a curved line reaching from the safe temperature Tsafe to the limit temperature Trisk is created, and a curved line from the limit temperature Trisk to the safe temperature Tsafe is created by repeating the above-described method. The wavy curved lines are drawn by repeating the curved lines increasing and decreasing between this limit temperature Trisk and the safe temperature Tsafe.

In the curved lines ( 1 ) to ( 3 ), a period where the environmental temperature T increases from the safe temperature Tsafe to the limit temperature Trisk is time when a continuous access to the nonvolatile memory device 100 H is possible, and is represented as the transmittable time trw. In the drawing, the transmittable times trw of the curved lines ( 1 ) to ( 3 ) are shown as transmittable times trw 1 to trw 3 , respectively. Meanwhile, the curved lines ( 1 ) to ( 3 ) corresponding to three access rates are shown here as an example in FIG. 36 , however, the access device 200 I actually selects one access rate that coincides with own access rate or that does not exceed own access rate and is the highest, and derives a curved line corresponding to this selected access rate.

Additionally, in the judgment at S 403 of FIG. 35 , a comparison between the temperature T and the limit temperature Trisk or a comparison between the transfer time t and the transmittable time trw is carried out. However, for example, according to the curved line ( 1 ) of FIG. 36 , when time the nonvolatile memory device 100 H is continuously accessed exceeds the transmittable time trw, the temperature T exceeds the limit temperature Trisk at the same time, and accordingly the temperature T of the nonvolatile memory device 100 H does not exceed the limit temperature Trisk when data writing and reading is controlled so that the time of a continuous access cannot exceed the transmittable time trw.

The access device 200 I calculates the transmittable time trw on the basis of the curved lined shown in FIG. 36 after setting the access rate in the access rate setting at S 400 of FIG. 35 . For example, in a case where a curved line corresponding to the access rate of the access device 200 I is the curved line ( 1 ), the transmittable time trw is time shown by the transmittable time trw 1 from the safe temperature Tsafe to the limit temperature Trisk. In a case of the curved line ( 2 ) or ( 3 ), the transmittable time trw is the transmittable time trw 2 or trw 3 , respectively. In addition, the access device 200 I has the display part 214 , and is able to display the selected access rate, the temperature parameter, and the transmittable time.

Three types of the curved lines of FIG. 36 were explained as curved lines showing temperature changes of three different access rates, however, similar to FIG. 36 , three types of curved lines may be obtained regarding three different types of nonvolatile memory devices of the same access rate. This is because that the temperature increase varies depending on the nonvolatile memory device, and it accordingly could be that the transmittable time trw varies even at the same access rate.

Additionally, also in this embodiment, since the access rate is determined to be the limit temperature Trisk or less, the temperature T does not usually exceed the temperature Trisk at steps S 403 and S 404 . In the above-mentioned manner, the nonvolatile memory device 100 H is accessed.

As described above, a temperature of the nonvolatile memory device 100 H is kept at the limit temperature Trisk or less by intermittently reading and writing data from and to the nonvolatile memory device 100 H on the basis of the access rate and the transmittable time. In this manner, the nonvolatile memory device, and the host device, and the nonvolatile memory system which eliminate a risk of a burn and which can read and write data at a high speed can be provided.

Tenth Embodiment

FIG. 37 is a block diagram showing a nonvolatile memory system according to a tenth embodiment of the present invention. The nonvolatile memory system of the present embodiment is configured by including an access device 200 J and a nonvolatile memory device 100 J. In FIG. 37 , the same numerals as those of FIG. 28 show the same components as those of the eighth embodiment.

FIGS. 38A and 38B are views showing moving image recording modes included in the access device 200 J. A codec part 217 of the access device 200 J has M kinds of modes where bit rates are from 8M bps to 24M bps as shown in FIG. 38A , or has M kinds of modes where frame rates are from 15 fps to 60 fps as shown in FIG. 38B .

In the present embodiment, after an access rate is set in the similar manner to the eighth or ninth embodiment, the codec part 217 selects a mode showing a bit rate or a frame rate satisfying a determined access rate from FIG. 28A or FIG. 38B . After that, compressed data generated by the codec part 217 on the basis of the selected mode is written to the nonvolatile memory device 100 J. Operations other than this operation are the same as those of the eighth or ninth embodiment.

Here, the codec part 217 generates compressed data by using an algorithm, for example, MPEG2 and MPEG4. A change of bit rate and a change of frame rate can be realized, for example, by changing: a quantization bit number of data; intervals of I-pictures; and the number of inserted P-pictures and B-pictures.

As explained above, the temperature T of the nonvolatile memory device 100 J can be kept at the limit temperature Trisk or less by determining a bit rate or a frame rate of moving image on an access rate and writing data to the nonvolatile memory device 100 J. In this manner, the embodiment can provide the nonvolatile memory device, and the host device, and the nonvolatile memory system which eliminate a risk of a burn and which can record moving image without stopping the recording because of heating.

Meanwhile, in a case where a relationship of each type of the nonvolatile memory device between an access rate and a temperature change of the nonvolatile memory device 100 J is approximately constant, when the access device 200 H, 200 I, and 200 J retain a temperature parameter of the nonvolatile memory device for each type of the nonvolatile memory device, an effect of the present invention can be obtained even if an access rate control is carried out on the basis of the temperature parameter value.

In addition, when a temperature sensor is used in the first to tenth embodiments, a type of the sensor is not limited, and it goes without saying that various types of sensors such as a contact or noncontact sensor, a thermistor, and a thermocouple can be used.

Moreover, the nonvolatile memory system of the above-mentioned fourth embodiment is characterized in that when a size of data to be read or written is preliminarily known, reading and writing of data is carried out after an access rate is determined based on the size so that the temperature T does not exceed the temperature Trisk. The nonvolatile memory system of the fourth embodiment is accordingly suitable for usage of dubbing data already recorded in another recording medium, namely, usage where a size of data to be recorded is preliminarily known. The nonvolatile memory systems of the other embodiments are suitable for usage of recording a moving image and the like in real time, namely, usage where a size of data to be recorded is not preliminarily known.

Meanwhile, the access device 200 B includes the cooling part 204 in the second embodiment, however, the cooling part may be included in the other embodiments. In addition, even in a case where the access device does not include the display part 201 , the effect of the present invention can be obtained. A user can know a state of the nonvolatile memory device from the status information displayed on the display part 201 without the cooling part 204 . The user can accordingly handle the nonvolatile memory device so that a temperature thereof cannot increase too much.

A nonvolatile memory system according to the present invention proposes a method for managing heat of a nonvolatile memory caused by high-speed data reading and writing not to be dangerous for a user. Not to mention a semiconductor memory card, this is beneficial for: a still image recording and reproducing device and a moving image recording and reproducing device using the nonvolatile memory device such as the semiconductor memory card; or a mobile phone.