JPH04205486A - Microcomputer with built-in prom - Google Patents

Abstract

PURPOSE:To prevent the contents of a PROM from being read out by a third person by providing this microcomputer(MC) containing the PROM with an offset value adding means for adding an offset value to an address applied from the outside of the MC and setting up the added value as the address of the PROM. CONSTITUTION:In the case of writing/reading data in/from the PROM 2 of the MC 9, an offset value should be written in an offset register 6 at first. The writing/reading of data in/from the PROM 2 after writing the offset value in the register 6 is executed similarly to a convensional MC with a built-in PROM, but differently from the convensional PC, a value obtained by adding the offset value stored in the register 6 to an address inputted from the external by an adder 7 is added to the PROM 2 built in the MC. Consequently it is difficult for a third person to correctly read out data written in the PROM 2 and the PROM data can be protected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a FROM-embedded microcomputer with excellent confidentiality.

[Conventional technology]

Figure 8 is a configuration diagram of a conventional FROM internal microcontroller.
Iejl1 person uses a specific fiijl (ROM writer, etc.)
” can be used to store information even when power is not supplied.
-Glogura that can be held! Pull ROM (hereinafter referred to as FROM
ICb"V+, lRj tl shown below ~11
$1 and the F ROM' internal microcomputer, which consists of a microcomputer core and peripheral circuits that perform data processing and control, (!1 is FROM, -m+HP ROMlt
141 is an address input path for incrementing the address of data to be read or written to
M,! A data input/output bus outputs the data written to or read from I, and Ml is a 4Ii911 bus that controls the writing of data to FROM.
! It is.

In addition to normal operations for general calculations and control a1, a microcomputer with built-in FROM has a FROM write mode (hereinafter referred to as "write mode") in which f-pt is written to puOM+t+, and a FROM mode in which to read the written data. Readout mode C and below, readout mode and Necho) f! - (both modes are collectively referred to as FROM mode). The data written into the FROM 41 in the write mode can be read out in the read mode to verify whether the written data is correct.

) ROM'! I'm pretty sure about the operation of writing data to +. First, enter the pot loading mode by means not shown in Figure 1. Next, add the address to the address input path 13), add the address to the data input/output path +411C data r4, and add the address to the 4F
Is there a write signal on the write signal control line 16)? When it is given, the data given by the data input/output path 41 is stored in the address given by the address input pass 13.

The previous work on reading data from F ROM and Il will be explained. First, read mode is set by means not shown in Figure 1. Next, address input path ill! /
c address [When given, the data written to the address given by the address input path 431 is outputted by the data input/output path +41 vc ratio.

[Problem to be solved by the invention]

Since the conventional PROM internal microcontroller is configured as shown above, it is possible to output the data to the outside of the sound device via Vc in order to verify the stored data. Therefore, using a PROM writer or the like, the contents of the FROM can be easily disclosed and confidentiality (data protection) can be ensured, which is a problem.

Is this invention something like the above? This was done to solve the problem, and the purpose is to obtain a PROM-related microcomputer that prevents a third party from reading the contents of the PROMQ.

[Means to solve the problem]

When the FR0M built-in microcomputer according to the present invention writes and reads data to the FROM, it adds an offset of 1 to the address given from the outside of the FROM internal microcomputer, and sets the offset l'l71LI to the 1kFROM address. It is equipped with a calculation method.

[Effect]

The PROM relative microcontroller in this invention has an offset M71D:! ! By i means, FROM data is FR
Since the ROM data is mapped to a position shifted by the offset value to the address given from outside the microcomputer with the built-in OM, it is difficult for a third party who does not know the offset value to read the ROM data correctly.

[English example]

FIG. 1 shows a PROMP31E that is an embodiment of the present invention.
Shows a microcomputer. In Figure 1, 2(~6+k
The explanation is omitted because it is the same as that of Amano, which follows the rice promotion example. ,
61 is an offset register that holds fEt (Offsera),
7) An adder for adding the address given to the near address (3) and the offset value held in the offset register tel ic 11, #ll calculation fi to +81
, 61 FROM, with nolii power! This is an internal address input path for lK7 and VZt.

ts+ri above! 1 to (8) and 9 indicate microcomputers related to PROM, which are composed of a microcomputer and an Ayabe circuit that perform data processing, control, etc.

This PROM p'3 JE? Iko y rt, FR
OM:! The address given to 1 (the address given by the internal address input bus (8)) is the address given by the address input bus 31 and the offset register 16.
) is the offset value 1km calculator (7), which is 7.
It is calculated by 1D.

The next Vc#I work will be explained. When loading and unloading data to the FROM and Il of the PROM internal microcontroller (9), the offset register and Il are first set.
It is necessary to write an offset value to l.

After writing offset 1 direct to the offset register 161, the operation of writing and reading data to FROM2+[ is exactly the same as in the conventional PROM internal microcomputer, but unlike the OE conventional microcomputer, the PROM internal microcomputer according to the present invention performs the following operations: As mentioned above, the address given to FROM 21 is obtained by adding the offset value held in offset register 16) to the address input from outside m'D- by adder 7). Therefore, the same R
When the address of the OM0M booter 15I- is given to the address input bus to be read into the present invention and the conventional PROM internal microcontroller, the ROM data is mapped into the address space as shown in the fIJs diagram. First, the ROM data of the PROM-related microcomputer according to the present invention is mapped to the extent that the ROM data of the conventional FROM-related microcomputer is shifted by an offset value.

Set offset register 1g1 and set 9 offsets to 1
．． If the power is turned off, the contents will be lost.

When reading the ROM data written above, before reading the ROM data, set the offset [t-offset register 181 tic
If you do not write it again, you will not be able to read the correct data.

After prompting, 6 people decided to use the above offset value! fi
It is difficult to create the correct ROM data, and R
It is effective in protecting data stored in OMIC@.

Next, the method of setting the offset value to the offset register (6) will be explained.

One offset register is mapped to a specific address in the address space of the microcomputer in the FROM. Writing to the offset register is performed in write mode, similar to writing to FROM. When the PROMff1 microcontroller is set to the write mode, the address input bus 31Vc offset register (6) is given the K offset value to the data input/output bus 141, and the data 11 write signal is given to the data write l1tlIa line 61. The offset value is written into the offset register 16). Also, the offset value can be written into the offset register 161 in ways other than those described above.

For example, the present invention is also effective in a method in which offset [ is set in the offset register 161K by port input.

〔Effect of the invention〕

According to the invention as described above, since the offset value addition means is provided, it is difficult to correctly read out the data stored in the processor θ/FROM, and the ROM data is protected. Attended.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a microcomputer with a built-in FROM that is an embodiment of the present invention, Fig. 2 is a diagram showing a comparison of ROM data mapping between the present invention and a conventional microcomputer with a built-in FROM, and Fig. 8 is a diagram showing a conventional PROM. FIG. 3 is a configuration diagram showing a built-in i icon. In the figure, 1. ! l is PROM, 1lli7
141 is a data input/output bus, +6)
is the control line, 181 t'10,007 set register, +
71t: is an adder, Ill+#'i internal address input bus, and a microcomputer with a built-in 191dPROM. In each figure, the same or corresponding parts are indicated by the same reference numerals.

Claims (1)

[Claims] When writing and reading data to PROM, P
A PRO characterized in that it is equipped with an offset value addition means that adds an offset value to an address given from the outside of a microcomputer with a built-in ROM, and uses the offset value as an address of the PROM.
M built-in microcomputer.