JP4324149B2 - Emulator and development support system using it - Google Patents

Description

  The present invention relates to an emulator and a development support system using the emulator, and more particularly to a technique effective when applied to emulation of an MPU incorporating a flash memory.

  Due to advances in semiconductor manufacturing technology, particularly miniaturization, the scale of circuits mounted on semiconductor devices has increased, and in semiconductor devices that perform logical operations, in addition to the CPU (Central Processing Unit) that executes arithmetic processing, An MPU (Micro Processing Unit) in which peripheral circuits such as outputs, a cache memory, a ROM in which a program code is written, and the like are integrated on a single chip is used for many purposes.

  In order to develop a user system equipped with such an MPU, a development support system has been built to support both software and hardware and confirm the operation of the MPU.

  In such a development support system, an ICE (In-Circuit Emulator; hereinafter referred to as an emulator) incorporating a circuit necessary for debugging is connected to the user system via an interface cable, and the emulator is connected to a personal computer or the like. The user system is debugged in a state close to the actual product form by connecting to the host computer.

  In a conventional development support system, an emulator is connected to an MPU equipped with an evaluation chip (hereinafter referred to as an “evaluation chip”) that is partially different from the MPU installed in the product, and signals are externally transmitted. The operation state of the MPU is monitored or traced by inputting and monitoring a response to the input through a display or the like.

  However, in recent years, in order to meet various needs of users, a family of manufacturing a plurality of products in which an operating frequency, a memory capacity, a configuration of peripheral circuits, and the like are changed using the same CPU core has been promoted. In such high-mix low-volume production, it is necessary to reduce the number of man-hours and costs required for the development of this EVA chip. For this reason, a development support system that performs emulation using the same thing as the MPU installed in the user system that is the product is considered. It was.

  In this development support system, by enabling the emulator emulation module to support multiple types of MPUs, it is only necessary to develop MPUs used in actual products, thereby improving development efficiency and reducing development costs. be able to.

  Also, in recent years, since it is advantageous to cope with a wide variety of small-scale development, there is an increasing number of cases where a nonvolatile memory that retains information even when a power supply voltage such as a flash memory is cut off is used as a ROM. By using flash memory, etc., it is possible to shorten the development period required for ROM manufacturing and reduce development costs. In addition, changes in specifications and the like need to be changed once written. Even in this case, there is an advantage that it can be easily handled.

  For example, the following Patent Documents 1 and 2 describe an emulator used for developing a system using an MPU with a built-in flash memory, and the following Patent Document 3 easily changes the clock frequency supplied to the MPU. An emulator that can be described.

JP 2002-49504 A JP 2004-341802 A JP 2004-139250 A

  In a nonvolatile memory cell used for a flash memory or the like, information is written or erased by injecting / releasing electrons to / from the floating gate of the memory cell. Since the insulating film is affected, repeated rewriting of information over time may cause the gate insulating film to gradually deteriorate, which may make the operation of the memory cell unstable or impossible.

  For this reason, in order to avoid troubles due to malfunctions of memory cells over time, the number of data rewrites is limited for each block, and the flash memory built in the MPU assumes the storage of programs etc. Therefore, the number of rewrites is about 1000 times.

  However, since flash memory is non-volatile and rewritable, it is increasingly used for recording data codes in addition to recording data such as program codes that are not frequently rewritten.

  In the development stage, the program code or data code is frequently written in the flash memory, and operation verification is frequently performed. However, if the frequency of rewriting increases, use of blocks that exceed the guaranteed number of times of rewriting must be stopped. In some cases, the MPU needs to be replaced.

  For this reason, in the technique described in Patent Document 1, when connecting the emulator, the connection to the bus for connecting each component in the LSI is switched from the internal bus connected to the built-in flash memory to the external bus and connected to the external SRAM. There has been proposed a technique for rewriting the SRAM without rewriting the built-in flash memory.

  When the alternative memory is used, as shown in FIG. 1, the MPU 2 dedicated to emulation mounted in the emulator 1 is connected to the alternative memory 4 by the dedicated external bus 3, and the MPU 2 is connected to the development object by the cable 5. The user system 6 is connected, and the MPU 2 functions in the same manner as in the state where the user system 6 is mounted.

  The MPU 2 is connected to the emulation module 7 of the emulator 1 by serial communication such as JTAG (Joint Test Action Group) standard, for example, and a terminal interface 8 is connected to the emulation module 7. A user operation terminal 9 is connected to allow the user to operate the emulator from the outside.

  The emulation module 7 incorporates a circuit necessary for debugging the program in order to process the entire emulation. In the emulation, various control signals for emulation are sent from the emulation module 7 to the MPU 2, information according to the internal state of the MPU 2 is received, the operation state of the MPU 2 is monitored or traced by the emulation module 7, and the user system 6 can be used to debug software such as programs.

  However, in this technique, a configuration for switching to the dedicated external bus 3 needs to be incorporated in the MPU 2 in advance, and the MPU 2 dedicated for emulation is required.

  As the scale of programs to be stored has increased with the increase in functionality of MPU, the built-in flash memory has been miniaturized to increase the capacity, and with the progress of such miniaturization, The number of rewritable times tends to decrease, which may become a more important problem in the future.

  An object of the present invention is to solve these problems and provide a technique capable of reducing the number of rewrites in emulation for a nonvolatile memory such as a flash memory built in an MPU. The above and other problems and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
In an emulator connected to a user system using an MPU equipped with a built-in flash memory, a cache memory corresponding to the memory space of the built-in flash memory is connected to the emulation module of the emulator. Perform emulation on behalf of functions.

  In a development support system for developing a user system product using an MPU equipped with a built-in flash memory, an emulator emulation module connected to the user system has a cache memory corresponding to the memory space of the built-in flash memory. Connected and this cache memory performs emulation in place of the function of the built-in flash memory.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
(1) According to the present invention, the function of the built-in flash memory can be substituted by the cache memory.
(2) According to the present invention, the effect (1) has an effect that the number of rewrites of the built-in flash memory can be reduced.
(3) According to the present invention, due to the effect (1), there is an effect that reading / writing of data can be speeded up.

  Embodiments of the present invention will be described below. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  FIG. 2 is a block diagram showing an example of a user system that performs development using an emulator according to an embodiment of the present invention.

  The user system 6 includes an MPU 10 with a built-in flash memory, and the MPU 10 performs various controls of the user system according to a program written in the built-in flash memory 11.

  FIG. 3 is a block diagram showing an example of a development support system constructed using an emulator according to an embodiment of the present invention. The MPU 10 mounted on the emulator 1 of the present embodiment is actually used as a product in the user system 6 and includes the same flash memory 11 as the product. The MPU 10 is connected to the user system to be developed by the cable 5 and functions in the same manner as the state mounted on the user system.

  The MPU 10 is connected to the emulation module 7 by serial communication such as JTAG (Joint Test Action Group) standard, for example. The emulation module 7 incorporates a circuit necessary for debugging the program in order to process the entire emulation. It is.

  In the emulation, various control signals for emulation are sent from the emulation module 7 to the MPU 10, information corresponding to the internal state of the MPU 10 is received, and the operation state of the MPU 10 is monitored or traced by the emulation module 7, and the user system 6 can be used to debug software such as programs.

  The emulation module 7 is connected with a cache memory 12, a valid table 13, a rewrite count counter 14, a compare module 15, and a terminal interface 8. A user operates the emulator from the outside to the terminal interface 8. A user operation terminal 9 is connected.

  FIG. 4 shows the relationship among the built-in flash memory 11, the cache memory 12, the Valid table 13, and the rewrite count counter 14. The built-in flash memory 11 is divided into a plurality of blocks each having a capacity of, for example, 4 KB, 16 KB, 256 KB, etc., depending on the application, and the total capacity is, for example, 32 MB. Have been identified.

  The cache memory 12 substitutes the function of the built-in flash memory 11 during a series of user operations for performing emulation, and therefore secures the same number of blocks and the same storage capacity as the built-in flash memory 11. However, in order to perform the function, it is sufficient that the memory space corresponding to the memory space of the built-in flash memory 11 can be constructed in the cache memory 12, so that the capacity of each block, the number of blocks, or the total capacity must be the same. There is no.

  The cache memory 12 is not limited in characteristics, and a flash memory may be used similarly to the built-in flash memory 11. However, other types of memory such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access) are used. Memory) or the like can be used, and the emulator price can be reduced by using the free memory of the emulator system. When a DRAM or SRAM is used as the cache memory 12, a high-speed response is possible when reading or writing.

  Since the normal internal flash memory 11 does not assume frequent data rewrite, the number of rewrites is about 1000. When the flash memory is used as the cache memory 12, it is used for data storage or the like. A general-purpose flash memory whose rewrite frequency is enhanced to about 100,000 times is desirable.

  The Valid table 13 corresponding to each block of the built-in flash memory 11 records the validity of the data in the cache memory 12 and records a value of “1” or “0” for each address. In this form, when the value of the Valid table 13 is “1”, the data in the cache memory 12 at the corresponding address is valid, and when it is “0”, the data in the cache memory 12 at the corresponding address is valid. Indicates that it is not valid.

  The rewrite count counter 14 records the number of rewrites 0 to N (N is a natural number) of the built-in flash memory 11 for each block. The rewrite counter 14 needs to retain data even when the power is turned off, and it is desirable to use a non-volatile memory from the viewpoint of maintenance and repair. For example, when a part of each block of the built-in flash memory 11 is open to the emulator 1, that part can be used as the rewrite count counter 14.

  FIG. 5 shows the operation of the compare module 15. The data read from the built-in flash memory 11 in the designated address range is compared with the data read from the cache memory 12, and the data matches or does not match. Is provided to the emulation module 7.

  FIG. 6 is a flowchart showing the operation of the emulator 1. First, when the emulator 1 is activated, the cache memory 12 is initialized as an initial operation, and then all the values in the Valid table 13 are set to “0”, and a command from the user operation terminal 9 is accepted. The initialization of the cache memory 12 is a value indicated by the built-in flash memory 11 at the time of all erasure, and normally the value is “1”.

  Here, when a “read data of address A” command is received from the user operation terminal 9, first, the value of the Valid table 13 corresponding to the address A is checked, and when the value is “1”, the cache Since the memory 12 is hit, the contents of the cache memory 12 corresponding to the address A are read and a response is returned to the user operation terminal 9. When the value of the Valid table 13 is “0”, the cache memory 12 has a miss-hit, so the contents of the built-in flash memory 11 corresponding to the address A are read and a response is returned to the user operation terminal 9.

  When a command “write data to address A” is received from the user operation terminal 9, first, the value of the Valid table 13 corresponding to the address A is set to “1”, and the data is stored in the cache memory 12 corresponding to the address A. And a response is returned to the user operation terminal 9.

  When a “program execution” command is received from the user operation terminal 9, first, the value of the Valid table 13 corresponding to the address A is confirmed, a block whose value is “1” is searched, and the Valid table The compare module 15 compares the data in the cache memory 12 corresponding to the address of the block whose block is “1” with the data in the built-in flash memory 11.

  Subsequently, the data of the cache memory 12 of the block determined to be inconsistent by the compare module 15 is written to the corresponding built-in flash memory 11, and the value of the rewrite counter 14 of the block for which writing has been performed is incremented by “1”. After returning all the values in the table 13 to “0”, the program is executed and a response is returned to the user operation terminal 9.

  Further, when a command for “other processing” that does not include a memory operation is received from the user operation terminal 9, the process is performed as before, and a response is returned to the user operation terminal 9.

  In the development support system of this embodiment, the cache memory 12 substitutes for the function of the internal flash memory 11 during a series of user operations for emulation, and writing to the internal flash memory 11 occurs only immediately before program execution. Therefore, the number of rewrites of the built-in flash memory 11 can be reduced.

  Until now, since the read / write operation from the built-in flash memory 11 is slow, it has become a speed bottleneck. However, the Valid table 13 corresponding to each block of the built-in flash memory 11 includes the cache memory 12. Since the validity of the data is recorded, reading from the cache memory 12 increases and a high-speed response is possible.

  Further, the compare module 15 can know whether the data read from the built-in flash memory 11 matches the data read from the cache memory 12. For this reason, even if the data is rewritten on the cache memory 12, if the data stored from the cache memory 12 has the same value as the data on the built-in flash memory 11, it is unnecessary to rewrite. Can be eliminated. This is effective in practical use from the viewpoint of program locality.

  Since the rewrite count counter 14 records the rewrite count of the built-in flash memory 11 for each block, the correct rewrite count can be known for each block. For this reason, the built-in flash memory 11 can be utilized up to the limit of the guaranteed number of rewrites.

  FIG. 7 is a block diagram showing a modification of the present embodiment. In this example, the MPU 10 is an on-chip emulator in which what is actually used as a product is mounted on the user system 6. Yes.

  The MPU 10 is connected to the emulation module 7 of the emulator 1 by serial communication such as JTAG (Joint Test Action Group) standard, and the emulation module 7 is a circuit necessary for debugging the program in order to process the entire emulation. Is incorporated.

  In the emulation, various control signals for emulation are sent from the emulation module 7 to the MPU 10, information corresponding to the internal state of the MPU 10 is received, and the operation state of the MPU 10 is monitored or traced by the emulation module 7, and the user system 6 can be used to debug software such as programs.

The rest of the configuration is the same as in the above example. The emulation module 7 is connected to a cache memory 12, a valid table 13, a rewrite count counter 14, a compare module 15, and a terminal interface 8. A user operation terminal 9 is connected to allow the user to operate the emulator 1 from the outside.
Also with the configuration of this example, it is possible to obtain the same effect as the above-described example.

Although the present invention has been specifically described based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the scope of the invention. It is.
For example, in the above description, the present invention has been described using emulation as an example. However, the present invention can also be applied to cases where the built-in flash memory may be frequently rewritten, such as a system self-check function. It is.

It is a block diagram which shows the development support system using the conventional emulator. It is a block diagram which shows the user system which develops. 1 is a block diagram showing a development support system using an emulator according to an embodiment of the present invention. It is a figure which shows the relationship between a built-in flash memory, a cache memory, a Valid table, and the rewrite frequency counter. It is a figure which shows operation | movement of a compare module. It is a flowchart which shows operation | movement of the development system which is one embodiment of this invention. It is a block diagram which shows the modification of the development assistance system using the emulator which is one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Emulator, 2 ... Emulation exclusive MPU, 3 ... Dedicated external bus, 4 ... Alternative memory, 5 ... Cable, 6 ... User system, 7 ... Emulation module, 8 ... Terminal interface, 9 ... User operation terminal, 10 ... MPU, DESCRIPTION OF SYMBOLS 11 ... Built-in flash memory, 12 ... Cache memory, 13 ... Valid table, 14 ... Rewrite frequency counter, 15 ... Compare module.

Claims (5)

In an emulator that connects to a user system that uses an MPU with built-in flash memory,
An emulator in which the emulation module of the emulator is connected to a cache memory corresponding to the memory space of the built-in flash memory, and the cache memory performs emulation in place of the function of the built-in flash memory. In a development support system that develops user system products using an MPU with built-in flash memory,
A cache memory corresponding to the memory space of the built-in flash memory is connected to the emulation module of the emulator connected to the user system, and the cache memory performs the emulation in place of the function of the built-in flash memory. Development support system that uses an emulator.   The development support system according to claim 2, further comprising a table for determining whether the cache memory is valid or invalid for each block of the flash memory.   4. The development support system according to claim 2, further comprising a module that compares the data recorded in the cache memory with the data recorded in the built-in flash memory to determine whether the data matches or does not match. .   The development support system according to any one of claims 2 to 4, further comprising a counter that records the number of times of writing in the built-in flash memory.

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