JPS61249154A - External memory device - Google Patents

Abstract

PURPOSE:To execute the highly speedy access and the data renewal, to prevent the reducing of the reliability and to execute the data transferring in a short time by providing the electric deleting rewritable type nonvolatile semiconductor memory, etc., and executing the data transferring control. CONSTITUTION:Immediately after a memory cassette 12 is fitted, all data are transferred from a nonvolatile semiconductor memory 11 to a volatile semiconductor memory 15 by a control device 16. For the access of the data from the main system, the highly speedy access can be executed by using the memory 15. Immediately before the device electric power source is interrupted, the data are transferred from the memory 15 to the memory 11 by the device 16. In that case, the memory cell group in the memory 11 corresponding to the area of the data renewed by the main system prior to the data transfer is deleted. Namely, out of all data of the memory 15, the renewed data area only can be written to the memory 11. Thus, the highly speedy access and the data renewal can be executed, the reduction of the reliability can be prevented and the data transferring can be executed in a short time.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an external storage capacity used in small combinations, computer systems, office automation 9.7 equipment, etc.
In particular, the present invention relates to an external storage device using a resilient semiconductor memory 2 and a nonvolatile semiconductor memory as storage media.

[Technical background of the invention]

Recently, a 3.5-inch microfloppy disk device, for example, has been commercialized as an external storage device for small combinations, computer systems, and the like.

This is expected to become popular as a small external storage device in the future because the disk serving as the storage medium is housed in a durable case and is easy to handle. On the other hand, in the field of inexpensive R-5 machines, ROM cassettes containing ultraviolet erasable and rewritable read-only memories (EPROMs) are used as software distribution media.

[Problems with background technology]

By the way, the micro-floppy disk device accesses data by mechanically moving the magnetic head, so the access speed is slower than that of semiconductor memory, and the data is accessed by keeping the magnetic head in close contact with the storage medium. Therefore, both the medium and the head are subject to severe wear, resulting in problems such as low reliability during long-term use. In addition, the R
Since the OM case uses FROM, which cannot be electrically erased, it is difficult to use it as an external storage device for updating data in principle.

In view of these circumstances, the applicant of the present application has developed a data storage system, which is capable of high-speed access and data updating, and whose reliability does not deteriorate even after long-term continuous use, in Japanese Patent Application No. 60-43913. Proposed. That is, the outline of this data storage system is to use a non-volatile memory cassette containing an electrically erasable/rewritable volatile semiconductor memory and a high-speed volatile semiconductor memory, and to use the non-volatile memory cassette as a storage device. The contents of the memory cassette are transferred to the volatile memory when the memory cassette is inserted into the main system, and the data is updated to the volatile memory when the main system is used. This is characterized in that the contents of the digital memory are electrically transferred to a non-volatile memory. When data in a volatile memory is transferred to a nonvolatile memory, only updated data is written, thereby increasing the speed of data transfer.

However, the above data storage system does not disclose any specific means for writing only updated data into the nonvolatile memory.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and is capable of high-speed access and data updating, does not reduce reliability even after long-term continuous use, and can be used with arbitrary non-volatile memory. The present invention provides an external storage device that can electrically erase a large area at the same time and transfer update data from a volatile memory.

[Summary of the invention]

That is, the external storage device of the present invention includes a nonvolatile semiconductor memory in which data can be written electrically and data in a large memory area of any size can be electrically erased, and a volatile semiconductor memory. , an interface device with an external main system, and a control device that controls these devices.

In this case, all data in the non-volatile semiconductor memory is sent to the volatile semiconductor memory immediately after the device power is turned on, and when the main system is used, the volatile semiconductor memory is accessed, and the volatile semiconductor memory is transferred immediately before the device power is turned off. It becomes possible to transfer the update data of the message to the non-volatile semiconductor memory.

In this case, non-volatile semiconductor memory has a function that allows rewriting only the required memory area, so the data transfer processing time immediately before the power is turned off is shortened, and the frequency of data rewriting is suppressed, which reduces the amount of time required. It is possible to extend the service life.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of an external storage device. 11 is an electrically erasable/rewritable non-volatile semiconductor memory, 12 PROM or 72. C,
It is assumed that a type FE2FROM or the like is used and has a capacity sufficient for an external storage device (for example, several hundred kilobytes or more). The non-volatile memory 11 is mounted on a board and housed in a mechanically rigid cassette case to form a memory cassette (see FIG. 2, 12), and the memory cassette 12 is inserted into a cassette case housing part of an external storage device. The storage and transportation of the memory cassette 12 is made possible by being able to be freely inserted into and removed from the memory cassette 12 and placed in an unloaded state (removed state). The non-volatile memory 11 is connected to a main system (not shown) via an interface device 13 (such as a cabin combination, a computer system, etc.), and is also connected to a volatile semiconductor memory 15 and a control device 16 via an internal path 14. has been done. As the volatile semiconductor memory 15, a dynamic, rectangular, or static type memory is used, and its capacity is approximately the same as that of the nonvolatile semiconductor memory 11.

The interface device 13 is connected to the internal path 14 and connected to the main system by a cable 2-in 17, and when the external storage device is accessed from the main system, the interface device 13 is connected to the internal path 14 and the internal path. The cable 2 is electrically connected to the path 14, and the cable 2
It plays the role of disconnecting the input 17 from the internal path 14. The control device 16 transfers data via the internal path 14 and the interface device 13
The controller is designed to transfer data from the non-volatile memory 11 to the volatile memory 15 immediately after the device is powered on, and to transfer data from the volatile memory 15 to the non-volatile memory 11 immediately before the device is powered off. It is something to be managed.

FIG. 2 shows an exploded appearance of an example of the external storage device, where 20 is a device housing sb, and inside this housing 20 is a volatile memory mounted with the volatile semiconductor memory 15. A control card 21 and a control card 22 equipped with the control device 16 and the interface device 13 are housed therein.

23 is a memory cassette holder with a plate, memory cassette 1
A female spring type connector 23 for receiving the board terminal portion 12b protruding from the cassette case 12 of No. 2.
A is provided, and this connector 23m is connected to the volatile memory card 21 and the controller 23m. - It is electrically connected to the board 22 and the like. The memory cassette 12 can be freely inserted into and removed from the tray 23 through a cassette insertion opening jOa provided on the front surface of the housing 20. 2
4 is the upper lid of the casing, which is provided with a heat radiation hole 241;
Inside the housing 20, although not shown, a power source such as a switch, a chingleg, a rotor, etc. is provided. The push-button switch 25 serves both to start the external storage device (for turning on the power) and to fix the inserted state of the memory cassette 12, and can perform OFF, OFF, and LOCK OFF operations with the memory cassette 12 inserted. It's supposed to be.

Although the external storage device in FIG. 2 is shown assuming that it will be installed separately from Main System, if it is built into the case of the main system, the case 20 and the top cover 2411C of the case Alternatively, it is possible to use a frame-shaped rack or the like, or to omit the power supply and use it as the main system power supply.

FIG. 3 shows a detailed configuration example of the program shown in FIG.
, a dynamic random access memory (DRAM) is used as the volatile memory 15, and each memory capacity is 1 Mbit, for example, by using 8 pieces of 1 Mbit memory.
It is set to bytes. As the control device 16, for example, an 8-bit microphone, four processors (MPU) j 1
, working memory 32, direct memory access (
It has a DMA) controller 33, and uses a read-only memory (ROM) storing a control program as the working memory 32 and a small-capacity RAM for a work area. The m French controller 33 is the FE2 controller.
This is to transfer data stored in PROM J1 or DRAM xs at high speed. The input/output port 34 is for interface with the main system, and the address expansion circuit 3゛5 is 8 pins) CP
This is for accessing the IM byte address space by U31. In addition, as CPU31, 16 bit,
) If you use a high-performance device such as a CPU, FE2FR
OM 11.

As the DRAM 15, a larger capacity one can be controlled.

Further, in the present invention, the non-volatile memory 11 is a memory chip which has a function of electrically erasing a certain area of any size simultaneously. That is, in the nonvolatile memory cell 11, the memory cell area is divided into first to fourth memory cell groups 7'41 to 44, as shown in FIG. The decoder 45 encodes an external address signal φ for specifying whether to erase the
The decode output signal φ, ~φ4 selects one of the transistors 46 to 49 for switching between the erase signal φ and the groups 41 to 44 and turns it on, and the remaining three transistors are turned on. By turning off the transistors, it is possible to erase all the memory cells of one selected memory cell group all at once. Furthermore, by performing multiple selection when decoding the address signal φ, it becomes possible to erase two or more memory cell groups at the same time. In addition, in FIG. 4, the memory cells are divided into four groups for the sake of simplicity, but when using a large-capacity nonvolatile memory as a large-capacity external storage device, the bit-configured memory If an integrated circuit is divided into several hundred to several thousand memory cell groups, the number of pits in one memory cell group will be on the order of several thousand to several tens of thousands of pits.

The above external storage device is a memory cassette.

Immediately after the device is powered on with the memory card 12 attached, all data is transferred from the nonvolatile memory 11 to the volatile memory 15 by the control device 16. Since the volatile memory 15 is used for data access from the main system, high-speed access is possible. That is, data is read from or written to an address in the volatile memory 15 specified by the main system. Then, data is transferred from the volatile memory 15 to the nonvolatile memory 11 by the control device 16 immediately before the device power is cut off. In this case, in this embodiment, prior to the data transfer, a nonvolatile memory corresponding to an area of data updated by the main system out of all the data previously transferred from the nonvolatile memory 711 to the volatile memory 15 is used. Control is performed by the control device 16- to erase the memory cell group located in the area of the memory 11.

That is, the address signal φ specifies the size or start address of the area to be erased (in other words, the memory cell group f to be erased). This makes it possible to write only the updated data area out of all the data in the volatile memory 15 to the nonvolatile memory 11. After data is written in the nonvolatile memory 11 in this way, by removing the memory cassette 12, it becomes possible to store, transport, etc.

The external storage device described above is an electrically erasable and rewritable non-volatile memory that can be written at high speed and has a high capacity that can be increased due to high integration. It is possible to reduce the price and reduce the price.
For example, 19
DIGEST OF TECHNICAL PAPER at the 1985 International Solid State Electronic Circuits Conference (ISSCC)
8P, 168~169°@A 256K F1a5h
EEPROM using Triple@Poly-
This FE2FROM has a different memory cell structure than the conventional E2FROM, including a control gate, floating foot, and erase f.
-) By using a one-transistor type memory cell, high-speed writing and high integration are possible.

According to the external storage device as described above, access from the main system can be performed faster than when using a B-disc device. This is because when using a floppy disk device, it takes several milligrams to move the magnetic head between the disks, but when using semiconductor memory, this waiting time is unnecessary. According to the external storage device of the present invention, an access speed comparable to the access time to the main storage device can be obtained.

Furthermore, according to the external storage device, the magnetic head and the storage medium are not used in close contact with each other as in the case of a single-disk device, so there is no wear even during long-term use, and the reliability is high. improves.

Furthermore, the external storage device allows data to be updated, unlike a ROM cassette, and can be applied as an external storage device for microcomputer systems and the like.

Moreover, according to the external storage device of the present invention, since the nonvolatile memory has a function of electrically erasing a certain area of any size at the same time, updating from volatile memory to nonvolatile memory is possible. It becomes possible to transfer data, it becomes possible to complete the data transfer in a short time before the non-volatile memory partially retrieves it, and it is also possible to suppress the frequency of rewriting data in the non-volatile memory. However, it is possible to extend its lifespan.

〔Effect of the invention〕

As described above, according to the external storage device of the present invention, high-speed access and data updating are possible, reliability does not deteriorate even after long-term continuous use, and the non-volatile memory used can be used with any size. The transfer can be completed in a short time by electrically erasing a large area of data at the same time and transferring the updated data from the volatile memory.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the external storage device of the present invention, FIG. 2 is a partially exploded perspective view of the external appearance of the device shown in FIG. 1, and FIG. FIG. 4 is a block diagram showing a specific example of the device shown in the figure. FIG. 4 is a circuit diagram taken out of the nonvolatile memory shown in FIG. 1 and showing an electrical erase signal input system. 11...Nonvolatile semiconductor memo I), 12...Memory cassette, 13...Interface device, 14...
・Internal space, 16... Volatile semiconductor memory, 1
6... Control device, 17... Cable line, 41~
44...Memory cell group, 45...Decoder, 46
~49...yDS for switch) transistor. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Main System II2! l! ! l No. 311! l bus node

Claims (5)

[Claims] (1) A nonvolatile semiconductor memory that can electrically write data and electrically erase data in a memory area of any size, and a connection between this nonvolatile semiconductor memory and the main system. an interface device provided, a volatile semiconductor memory connected to the nonvolatile semiconductor memory via an internal bus, and an interface device that controls the two types of semiconductor memories and the interface device, and controls data between the two types of semiconductor memories. An external storage device comprising: a control device for managing transfer; and a control device for managing transfer. (2) The external storage device according to claim 1, wherein the nonvolatile semiconductor memory is housed in a mechanically strong case, and the case is detachable from the external storage device. (3) External storage device All data in the nonvolatile semiconductor memory is transferred to the volatile semiconductor memory immediately after power is turned on, and data is transferred from the volatile semiconductor memory to the nonvolatile semiconductor memory immediately before the power is turned off. The external storage device according to claim 1, characterized in that: (4) The external device according to claim 1, wherein the control device causes the volatile semiconductor memory to read and write data from the main system when the main system is used. Storage device. (5) The nonvolatile semiconductor memory has a function mounted on the memory chip that allows the size or start address of the memory area to be erased to be arbitrarily specified during use. External storage device described in section.