JPS5878240A - Data processing device having program memory - Google Patents

Abstract

PURPOSE:To output the contents of an ROM to the outside and to protect the security of a program, by detecting an optional specific address given to the ROM and changing the contents of the program read out from the ROM when this specific address is detected. CONSTITUTION:A data processing unit consists of a CPU part 1 where a one- chip microcomputer is connected to an internal data bus 5, an RAM part 2, ROM part 3, and input/output circuit part 4, and the CPU part 1 and the ROM part 3 are connected by an ROM address bus 6. The ROM part 3 is provided with an ROM cell part 11 and address detecting circuit part 12 which are connected to an address bus 15, and an ROM output circuit part 13 is connected to the cell part 11 and the circuit part 12. A specific address given to the cell part 11 through the bus 15 is detected by the circuit part 12; and when this specific address is detected, the contents of the cell part 11 are changed and are outputted to an internal data bus 14 from the circuit part 13, thus protecting the security of a program.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data processing device that stores a program memory, and has a secret-keeping function that prevents a third party from easily using the program. The present invention relates to a data processing device.

There is an l-chip microcomputer as an alternative to the conventional data processing device that stores programs in a memory (hereinafter referred to as R (JM)) dedicated to alignment. Due to the lag, there are many cases in which a circuit that can output the R(7M contents to an external terminal) is installed. However, by having this function, huMO Uchitani is easily known by the It has the disadvantage of being overused.Also, if the function to output the contents of JM to an external terminal is deleted for security reasons, the contents of 90M will become untestable and the selection of microcomputers will be difficult. The defective yield of the time decreases.

The main party's purpose is to have the ability to attack the KOM0M content department and 7'C"ffi"! Therefore, the present invention aims to provide a data processing device having a function of storing n programs stored in a ROM.

The present invention has a specific address among the R(JM addresses) supplied to the kL(JM section) in the ROM in the microcomputer, and this specific address and 11.
(Compare the address given to KUM in the JM test and if the two match, then read n'kL
Output time to forcibly change the contents of OM! +8'fr included.

Next, some examples of the present invention will be described with reference to the drawings.

FIG. 1 shows the l-chiku-1 microcombination according to the present invention, -po
Bua,,/structure1i1. Ig with hD, CLJPii, ′
kLAM section 2. The RUM section 3, output section 4 is integrated on one chip, and connected to each other by an internal data bus 5. In addition, the R (JM address bus 6) is supplied from the CPU@1 to the 80M section. Fig. 2 is a block diagram explaining in detail a part of the 80M section of the original embodiment. Yoniku (JM cell part 11.
Address detection circuit section 12. The address bus is wired such that the address bus is supplied to the JM cell section 11 and the address detection circuit section 12.

The address detection circuit section 12 applies no more than n when the address matches. Basic operation H of the original example
e) The CPU section 1 operates according to the command in JM3, which is determined by the OM address output from the Li section 1. At this time, the contents programmed in the ROM section 3 are specified by the address. The signal is supplied from the 90M cell section 11 to the ePu section 1 via a circuit separate from the output circuit 13.

According to this example, h (when the same address as the nyc address programmed into the address detection U% during JM inspection is applied from the CPυ part l to the address detection circuit part n, the address detection circuit part outputs 90M tblJ control Ipo-go 16 is nine (JM
The input signal is applied to the output circuit 13, and an instruction different from the instruction read from the JM cell unit 11 is generated by the output -wr13. (Even if you specify the JM address, you cannot know the normal content.

That is, the microcomputer user has the ability to output the contents of the itOM section to an external terminal by programming the address of the buttress detection circuit at the same time as writing the program into the ROM section. It is also possible to maintain the confidentiality of the i-LCJM department's programs. Further, by preparing a plurality of n addresses Ovl to be set in the address detection circuit section, it becomes possible to maintain strong confidentiality. Similarly, when the user of the Meiyoke outputs the contents of the 80M part to the external terminal, he knows the address of the address detection circuit, so it may vary depending on the 70 (even if the JM internal answer is output, it is normal). It is easy to know the contents.In the same way, the operation of the address detection circuit section can be explained in 14 (the output of the Uchitani street of the 3M section may be outputted to the outside). do not have.

In addition, in order to maintain the confidentiality of the ROM department's program 6 answers,
The front 8d address detection circuit 4C can be detected by checking the outside of the chip microcomputer υ with a microscope and mirror.
There is no need to explain that the specific address can be programmed more reliably by using a method such as ion implantation technique that does not cause any difference in appearance.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a one-chip microcomputer according to an embodiment of the present invention.
FIG. 3 is a more detailed block configuration diagram of the section. l...CPU section %2...RAMg, 3
....i-1, (3M section, 4 .... input/output circuit section, 5 .... internal data bus, 6 ... address bus, 11 .... ...i-L (JM cell section. 12...Address detection circuit section, 13...
・I(, (JM output circuit section, 14...°internal data bus, 15...address bus, 16...
...R (JM output control signal.

Claims (1)

[Claims] In a data processing device having a program memory and a control circuit for outputting the contents of the program memory to the outside, means for detecting a ttX&-)% constant address among the addresses given to the program memory; v
A data processing device having a program memory, characterized in that the program memory comprises means for changing the contents read from the two-log memory when a specific address is detected by the instant address display means.