JPH03186927A - Program alteration device for microcomputer - Google Patents

Abstract

PURPOSE:To facilitate modification of a program by using program altering RAM incorporated in a one chip microcomputer, and a nonvolatile memory which is externally connected to the microcomputer, which stores program altering data and capable of serial communication. CONSTITUTION:When alteration address data A1 which is set in an address data area 11a coincides with the output content of a program counter 1, an output permission signal is transmitted from a coincidence detection means 13a to a vector table 12a and only the data output of the vector table 12a is transmitted to a program counter value alteration means 14. When the output of the coincidence detection means 13a is simultaneously inputted to an interruption generation circuit 16 through an OR circuit 15, interruption occurs and a vector address 1 from the vector table 12a is inputted to the program counter alteration means 14 by the interruption. The means 14 refers to the content AAAA of the vector address 1 and alters the content of the program counter 1 to AAAA. Thus, the content of a ROM program can easily be altered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microcomputer system, and more particularly to a microcomputer (hereinafter referred to as "microcomputer") that outputs modified program data in place of program data to be modified in a read-only memory. , abbreviated as microcomputer).

[Prior Art] Generally, a conventional one-chip microcomputer includes a program counter PC1, a program memory PM in which a predetermined program is written, and an instruction decoder ID, as shown in FIG. As is well known, the operation of this one-chip microcomputer is such that data successively outputted from a program memory PM whose address is specified by a program counter Pc counted up by a system clock (not shown) is decoded by an instruction decoder ID. The program is executed by

As the program memory PM, a mask ROM (read only memory) is numerically used, and a program is written into the mask ROM by the manufacturer during the manufacturer's manufacturing process, and cannot be rewritten by the user.

Furthermore, recently, a so-called one-time ROM, which can be rewritten only once by the user, is also on sale.

However, if a bug is discovered in the mask ROM writing program after manufacturing the one-chip microcontroller, or if you want to correct a part of it, it is necessary to rewrite the ROM mask pattern and restart the integrated circuit manufacturing process. Therefore, it currently takes several months to manually create a modified one-chip microcontroller.

Moreover, a one-chip microcomputer in which a bug has been found in the mask ROM writing program cannot be reused. Furthermore, one-time ROMs are much more expensive than mask ROMs, and it takes much time for a user to write a program, making them unsuitable for mass-produced products.

In order to solve these problems, the inventors of the present invention have developed an electrically writable non-volatile memory section for data rewriting into a one-chip microcontroller in accordance with "Japanese Patent Application No. 131861". A method to modify program data was proposed.

In this method, a program address to be modified and a location for storing the modified program are specified in an electrically writable non-volatile memory section in a one-chip microcontroller, and the program counter and the program address to be modified in the non-volatile memory section are specified. If there is a match, the update program will be executed.

By doing this, even if a bug in the program is discovered after mass production of the one-chip microcontroller, or if a part of it needs to be fixed, the program can be changed without having to modify the mask ROM again, eliminating the need to stop the production process. .

[Problems to be Solved by the Invention] Although the method described above can be realized with a relatively simple circuit configuration, it is usually
Since it is necessary to add an electrically writable non-volatile memory part into the one-chip microcontroller manufactured by the process, there is a problem in that the cost of the one-chip microcontroller increases as a result. . Furthermore, not all of the capacity of the built-in non-volatile memory section is used; in fact, all of it is often not used, resulting in wasted capacity.

In order to solve this problem, it is possible to use a microcontroller that can switch the port, address bus, and data bus and expand the program memory externally with a parallel data communication type device, but this is not possible. , which is undesirable in terms of effective use of ports.

The present invention was made with attention to such problems,
If a bug is discovered in the read-only memory write program in a one-chip microcontroller, or if you want to fix a part of it, you can modify the program by pseudo-writing a part of it without rewriting the read-only memory contents. Alternatively, it is an object of the present invention to provide a microcomputer program changing device that can substantially add or delete programs by performing interrupt processing, and that can realize a one-chip microcomputer using a CMOS process. shall be.

[Means for Solving the Problems] A microcomputer program change device of the present invention includes a one-chip microcomputer that operates according to program instructions stored in a read-only memory, and a non-volatile microcomputer connected to the one-chip microcomputer by a signal line. In the microcomputer system, the nonvolatile memory stores a change address and instruction code for changing the program in the read-only memory. receives the modified address and instruction code from the non-volatile memory and stores them in the random access memory, compares the modified address with the contents of the program counter, and if they match, executes the instruction code 2. I have to.

[Operation] When a bug is discovered in the writing program of the ROM in the Cowanchip microcontroller, or when you want to correct a part of it, the address data corresponding to the address to be corrected in this ROM and the corrected program data or the corrected program data are Program data for interrupts is stored in a non-volatile memory provided outside the microcontroller, and the stored data in the non-volatile memory is sent via the serial communication circuit using a command immediately after a reset when the one-chip microcontroller is powered on. Load into random access memory (RAM) for program modification. As a result, when the address data stored in the RAM for program modification and the program counter match, the modified program data stored in the RAM for program modification is used instead of the program data to be modified in the ROM. Interrupt processing is now performed based on the program data output to the instruction decoder or for interrupts, and a program with bugs and the like corrected is executed. In addition, in interrupt processing, it is possible to change the flow of processing up to that point by rewriting data in memory, calling a subroutine for a function you want to add, or unconditionally jumping, and essentially adding or deleting a program. Yes, it is possible to modify the program.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the concept of the microcomputer program changing device of the present invention will be explained with reference to FIG. In the microcomputer system shown in FIG. 1, 10 is a one-chip microcomputer, and 20 is an electrically writable nonvolatile memory that is provided outside the microcomputer 1o and stores data to be set in the one-chip microcomputer 10. , 30 is a signal connecting the microcomputer 1o and the nonvolatile memory 20! (For example, serial communication wiring).

In the one-chip microcomputer 10, 1 is a program counter, and 2 is a mask R in which a predetermined program is written.
OM, 3 is RAM for program change, 4 is selector, 5
is an instruction decoder, 6 is a RAM for main memory, and 7 is a serial communication circuit, which is connected to the nonvolatile memory 20 via the wiring 30.

The program counter is connected not only to the ROM 2 but also to the program changing RAM 3 so as to provide an address value.

The program change RAM 3 is used to store address data corresponding to the address to be corrected and program data for correction when a bug is discovered in the program written in the ROM 2 or when a part of it is desired to be corrected. It has a change address RAM 31 and a program RAM 32 in which changes are written. These address data and program data are stored in the nonvolatile memory 2o so that the data stored in the nonvolatile memory 2o is read by serial communication via the serial communication circuit 7 in response to a command immediately after a reset when the one-chip microcomputer 10 is powered on. The program change RAM 3 is substantially equivalent to a non-volatile memory.

The selector 4 normally selects the output data of the ROM 2 and inputs it manually to the instruction decoder 5, but the selector 4 selects the output data of the ROM 2 and manually inputs the data to the instruction decoder 5.
M3] - When the address data stored in - and the output contents of program counter 1 match, the program RA
When program data is output from M32, the output data of the program RAM 32 (corrected program data) is selected in place of the output data of the ROM 2 (program data to be corrected) and the instruction decoder 5 is manually operated. There is.

On the other hand, the non-volatile memory 20 may include an electrically erasable EEFROM, an ultraviolet erasable EFROM, a one-time FROM, and a normal RAM with a backup battery.
However, here, we use EEPRO that can communicate serially.
It shows M.

In this case, recent camera systems use E, F ROM to store adjustment data after product assembly.
In addition, the price per bit capacity of EEFROM has come down considerably. Therefore, if the remaining portion of the EEFROM other than the adjustment data storage section is used for storing program change data, the program can be changed without increasing the cost of the product.

FIG. 2 shows an example of a data map of the EEFROM 20. In other words, the area up to a predetermined address in the EEPROM 20 is the adjustment data area, and the subsequent addresses (
Here, the area after address "hhh" is determined to be the program change data area. This program change data area is divided into a change address data area, a change program capacity data area, and a change program data area. The data format of the program change data area is a set of change address data in the change address data area, change program capacity data in the change program capacity data area, and change program data in the change program data area.

1 In other words, in the changed address data area, “h
First change address data A1 that you want to change to address hh”
, then set the second change address data A2, the third change address button A3, ... if the m-th change address data Am exists, successively set it after the "hhh" address. do. In this case, it is assumed that the number of correction points in the microcomputer is determined in advance to be m depending on the capacity of the change address RAM. Therefore, the microcontroller can change m locations in the program, but if the number of modified address locations is less than m, the ROM address that will never be modified, for example, data such as 0000(H), will be changed to the modified address data. It is sufficient to configure the hardware of the microcomputer so that it is set in the remaining part of the area and the ROM program is not modified in the case of this address 0000 (H).

In addition, in the changed program capacity data area, “
After address hhh10m'', modified program capacity data B1 to Bm indicating the capacity (length) of the modified program that is paired with the first modified address data A1 to the m-th modified address data 2Am are sequentially set.

In this case as well, if the number of changed addresses is less than m, the remaining part of the changed program capacity data area is filled with 0.
Set the data of 000 (H).

In addition, in the change program data area, “hh
The first changed address data A after address "h+2m"
1- Change program data C1 to Cm indicating the contents of the change program paired with the m-th change address data Am are sequentially set. Here, the starting address of the modified program data C2 is "hhh+2m+Bl+1", and the starting address of the modified program data Cm is "hhh 1,000 2m".
+810B2+-B (m-1)+1" address.

In this case as well, if the number of changed addresses is less than m, the rest of the changed program data area is filled with 0OO.
Set the OH data.

Next, the operation of the microcomputer shown in FIG. 1 will be explained. The operation of this microcomputer is basically the same as that of the conventional microcomputer 3, but in addition, a part of the program written in the ROM 2 is artificially rewritten to modify the program. In other words, E as described above
The data in the program change data area of the EPROM 20 is read by serial communication via the serial communication circuit 7 and set in the program change RAM 3 in response to a command immediately after the one-chip microcomputer 10 is reset when the power is turned on. In this case, the modified address data in the modified address data area is sequentially set in the modified address RAM 31, and the modified program capacity data in the modified program capacity data area and the modified program data in the modified program data area are sequentially set in the program RAM 32. Normally, data read from the ROM 2 whose address is specified by a program counter 1 counted up by a system clock (not shown) is selected by a selector 4 and sent to an instruction decoder 5.
The program is executed by being decoded by However, when the address data stored in the changed address RAM 4 3] and the output contents of the program counter 1 match, the program RAM
When the block diagram data is output from the program RAM 32, the output data of the program RAM 32 (corrected program data) is selected by the selector 4 and input to the instruction decoder 5 instead of the output data of the ROM 2 (program data to be corrected). As a result, the pseudo-rewritten program is decoded by the instruction decoder 5, and the modified program is executed.

Next, a first embodiment of the present invention will be described. FIG. 3 shows a specific example of the modified address RAM 31, and FIG. 4 shows a memory map when the ROM 2 and the program RAM 3 are arranged in the same address space.

The modified address RAM 31 shown in FIG. 3 has address data areas 1.1a to 1.1. m, vector tables 12a to 12m, and matching detection means 13a to 13m.

The above address data areas 1.1 a to ]-1 and m are set with the changed address data A] to Am, and vector tables 1.2 a to 1.2 m contain the start address ('') of the interrupt processing. 2. Changed address data A1-A
The data of vector addresses 1 to m of the program RAM storing the starting addresses of changed program data C1 to Cm paired with m are set.

The value of the program counter 1 is input to the plurality of sets of match detection means 13a to 13m, and when a match is detected in any of them, the matched address data area 11i
Vector table 12 of the same group as (a=1,...m)
1, and sends an output permission signal to the vector table 12i.
Only data output or program counter value changing means 14
can be conveyed to.

Further, each output of the plurality of pairs of coincidence detecting means 13a to 13m is input to the interrupt generation circuit 16 via the OR circuit 15, and if a coincidence is detected in any one of the plurality of pairs, and the contents of the interrupt permission flag are If 6 is permitted, an interrupt occurs, and the program counter value changing means 14 updates the vector table 1 of the matching set.
A value of 21 is written to program counter 1, and at the same time,
program counter] is saved to a stack (not shown). Furthermore, if the contents of the interrupt permission flag are prohibited, no interrupt occurs and the value of the program counter does not change.

In the memory map shown in FIG. 4, the address of the program RAM area is assigned following the address of the ROM area. In the program RAM candy area, following vector addresses 1 to m, change program data c1
~Cm are set sequentially. In this case, address data AAAA for jumping to the start address of the changed program data c1 is set in the vector address 1. Address data BBBB-MMMM for jumping to the start address of the changed program data C2-Cm is set in the vector address data 2-m. This address data B B B B-M
Immediately after reading data from the EEPROMs 20 to 7, the MMM is calculated according to the changed program capacity data and then reset.

Here, the sequence of changing the ROM program will be explained by taking the first set of change programs as an example.

First, changed address data A is set in the address data area 11a. When the changed address data A1 currently set in this address data area 11a matches the output content of the program counter 1, an output permission signal is sent from the match detection means 1.3a to the vector table 12a, and this vector table 12a is Only the data output (vector address 1 in FIG. 4) is transmitted to the program counter value changing means 14. At the same time, when the output of the error detecting means 13a is input to the interrupt generating circuit 6 via the OR circuit 15, an interrupt occurs, and this interrupt causes the vector address 1 from the vector table 12a to be changed to the program counter value changing means 14. Here, the content of the program counter 8 is changed to AAAA by referring to the content AAAA of the vector address 1. Therefore, the modified program data B1 of the program RAM area addressed by the program counter 1 is selected by the selector 4 and input to the instruction decoder 5 instead of the output data of the ROM 2 (program data to be modified). As a result, the pseudo-rewritten program is decoded by the instruction decoder 5, and the first set of changed programs is executed.
The contents of the AA address will be substantially changed.

If you write a jump instruction to the address you want to return to in the ROM area on the last line of the above change program, you can change a program in ROM of any length to a program in RAM of any length. be able to.

Note that the change address RAM 31 shown in FIG. 3 uses the interrupt generation circuit 16 to give instructions to the program counter value change means 14, but the interrupt generation circuit 16 is not particularly required, and the OR 9 circuit 15 An instruction may be directly given to the program counter value changing means 14 by the output.

Next, a second embodiment of the microcomputer of the present invention will be described. This second embodiment focuses on the fact that, when actually correcting a bug in a ROM program, it is often enough to correct one or two lines of the program. is for modifying and running
Compared to the first embodiment, the data type of the EEPROM 20 (
The difference is that the data structure) has been changed as shown in FIG. 5, and the configuration of the program change RAM has been changed as shown in FIG. are doing.

That is, in the EEPROM 20, as shown in FIG.
The addresses after that are determined to be the program change data area. Then, in the program change data area, pairs of data at an address to be changed and one line of the change program are successively set as many pairs as the number of pairs desired to be changed. In this case, the remaining part of the changed address data area contains 000 as described above.
0 (H) data is set.

Further, in the program change RAM, as shown in FIG. 6, a plurality (n) of data correction blocks 61 to 6n are provided corresponding to the desired number of data corrections.

In each of these blocks 61 to 6n, an address data area 62 and a program data area 63 are secured as a pair of memory areas, and this address data area 6
2 and the program data area 63, a modified address and data for one line of the modified program are correspondingly set by serial communication. In this case, the modified address and data for one line of the modified program are sequentially set in the data modification blocks 61 to 6n. Further, one pig judgment circuit 64 is provided for the address data area 62 and the program data area 63, and this data judgment circuit 64 is configured to detect the address input from the program counter 1 and the data stored in the address data area 62. When a match is found, a match signal output is activated, an output permission signal is given to the program data area 63, and an output permission signal is sent to the OR circuit 65. The output permission signal controls the output of the program data (modified data) stored in the program data area 63, and the output data (modified data) of each block 61 to 6n is sent to the selector 4 via a common bus. Data becomes human power.

Note that each block 61 to 6n has a different data modification location (address), so when data is modified, modified data is output from one of the blocks. Further, the output of the OR circuit 65 serves as a manual switching control for the selector 4, and the output of the OR circuit 65 serves as a switching control manual for the selector 4.
The output data of M is selected instead of the output data of ROM2 (program data to be corrected).

In the second embodiment described above, basically only a program having the same length or a shorter length than the ROM code can be changed. Here, an example of changing the code to a code having the same length as the ROM code is shown in FIG.

That is, for example, the 2-hide instruction code (9A, OE) starting from the ROM address 107A is converted to (9B, 3
When changing to the 2-byte instruction code D), for example, change addresses 1 and 2 of the EEPROM 20 as shown in the figure.
and a pair (1,07A, 9B) of the change address data and one line of the change program in change program 1.2,
(107B.

3D) in order.

FIG. 8 shows an example of changing the ROM code to a shorter code. That is, for example, when changing a 2-byte instruction code starting from ROM address 107A to a 1-byte instruction code C1, change the contents of either of the two ROM addresses to which the 2-byte instruction code is written to a NOP instruction code (for example, 00), and as shown in the figure, a pair (1
07A, CI) and (107B, 00)3 are written in sequence.

The 3-byte instruction code, etc. can also be changed in accordance with the above-mentioned change of the 2-byte instruction code.

Next, a method of changing the ROM code to a longer code in the second embodiment will be explained.

FIG. 9 shows an example of changing a 1-byte instruction code to a 3-byte instruction code.
The 1-byte instruction code C1 of A02 is (79, 46, B3
) shows the case of changing to a 3-byte instruction code. In this case, if a code of 9ASOE is written in ROM addresses 3AO3 and 3AO4, for example as shown in the figure, then the program change data area of the EEPROM 20 will have a change address 1 as shown in the figure. -11 and change programs 1-11 are used to continuously write a pair of change address data and one line of change program.

Here, it is assumed that the 1-byte instruction code 90 is an instruction to jump to the following 2-byte code, and the area after 4 ROM address cooo is an area that is not used by the program of the one-chip microcomputer of the present invention.

Next, a procedure for actually executing a program for changing the 1-byte instruction code C1 to a 3-byte instruction code (79, 46, B3) will be described.

First, when the data of ROM addresses 3A02 to 3A04 match the data of [change address] to 3 in sequence, code C1 is rewritten to code 90 at ROM address 3A02,
Code 9A and code C when ROM address is 3AO3
Since the code OE is rewritten to code 00 at ROM address 3A04, instruction code 90 is executed and jumps to ROM address cooo, which is not used in the program of the one-chip microcomputer of the present invention. Here, since the area after ROM address cooo is an area where there is no program, it may be used freely. Next, when the data of change addresses 4 to 6 sequentially match the ROM addresses cooo to C002, the 3-byte instruction code (7
9, 46, B3).

Next, when the data of the change address 7.8 sequentially matches the ROM addresses C003 and C004, the ROM address 3AO3, which was written in the change program 7.8,
The same code as the 2-byte code of 3AO4 (9A, OE
) will now be executed. Then, when the data of changed addresses 9 to 11 sequentially match the ROM addresses C005 to COO7, the jump command 90 written in the changed programs 9 to 11 and the jump destination (3A,
05) is executed and returns to ROM address 3AO5.

The above operation essentially means that the 1-byte instruction code is changed to a 3-byte instruction code and executed.

It goes without saying that by using the above-described modification method, it becomes possible to execute even longer programs instead of using ROM code.

6 [Effects of the Invention] As described in detail above, according to the microcomputer program changing device of the present invention, the program changing RAM built in the one-chip microcomputer and the external device connected to the microcomputer can transfer program changing data. By using the stored non-volatile memory that can be used for serial communication, the changed data stored in the non-volatile memory is read into the RAM for program changes via serial communication in response to a command immediately after resetting when the microcontroller is powered on. . As a result, if a bug is discovered in the ROM writing program or if you want to modify a part of it, you can modify the program by pseudo rewriting a part of it without rewriting the ROM contents, or use the interrupt By performing the processing, it is possible to substantially add or delete programs and modify the program.

Therefore, it is possible to reuse a microcontroller in which a bug has been found, eliminating the need to recreate the ROM, and without affecting the production process. can. In fact, when a bug is to be corrected, it is often enough to modify one or two lines of the program, so the microcomputer of the present invention is extremely useful.

Moreover, since the one-chip microcomputer can be realized using a CMOS process, the cost increase of the one-chip microcomputer can be suppressed as a result.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the concept of a microcomputer program change device of the present invention, FIG. 2 is an explanatory diagram showing an example of the data structure of the EEPROM in FIG. 1, and FIG. 3 is a first embodiment of the present invention. FIG. 4 is a block diagram showing a specific example of a program changing RAM used in the first embodiment of the present invention. FIG. 5 is an explanatory diagram showing the data structure of the EEPROM used in the second embodiment of the present invention, and FIG. 6 is a specific example of the program change RAM 8 used in the second embodiment of the present invention. FIG. 7 is a block diagram showing an example of the ROM code and EEFROM code when changing the ROM code to a code of the same length in the second embodiment of the present invention, and FIG. 8 is a block diagram showing the second embodiment of the present invention. In the embodiment, ROM
FIG. 9 shows an example of the ROM code and EEPROM code when changing the code to a shorter code, and FIG. 9 shows the ROM code and EEPROM code when changing the ROM code to a longer code in the second embodiment of the present invention.
FIG. 10, which shows an example of a ROM code, is a block diagram showing a conventional one-chip microcomputer. 1...Program counter, 2...ROM. 3...RAM for program change, 4...Selector,
5... Instruction decoder, 6... Serial communication circuit,
7...Nonvolatile memory, 1], a~l1m...
Address data area, 12a to 12m... Vector table, 13a to 13m... Match detection means, 14...
・Program counter value changing means, 15... OR circuit, 16... Interrupt generation circuit, 31... Change address 9 AM. Pudalam RAM. Address data area, 3... Program data area, 64... Data judgment circuit, 5... OR circuit.

Claims (1)

[Scope of Claims] A microcomputer system comprising a one-chip microcomputer that operates according to program instructions stored in a read-only memory, and a nonvolatile memory connected to the one-chip microcomputer by a signal line. The one-chip microcomputer receives the modified address and instruction code from the nonvolatile memory, and the one-chip microcomputer receives the modified address and instruction code from the nonvolatile memory. a receiving means; a random access memory for storing the modified address and the instruction code; a comparing means for comparing the modified address with the contents of the program counter; A program changing device for a microcomputer, comprising: instruction execution means for executing code.