JPS63115252A - Microcomputer constituting method - Google Patents

Abstract

PURPOSE:To constitute a microcomputer which has the chip area reduced as much as possible and has a memory superior in security by dividing a ROM and a PROM into plural blocks and alternately arranging them on consecutive addresses. CONSTITUTION:A ROM 3 is provided with a ROM matrix 9, and a PROM 4 is provided with a PROM matrix 12. Selecting circuits 11 and 15 of the ROM 3 and the PROM 4 select one word of the ROM 3 or the PROM 4 in accordance with information from a common address line to output data to a common data line 6. Selecting circuits 11 and 15 alternately arrange ROM areas and PROM areas on consecutive addresses. Thus, the microcomputer is constituted which has the chip area reduced as much as possible and has a memory superior in security.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of configuring a program memory suitable for improving the confidentiality of a program of a microcomputer incorporating an OM.

[Conventional technology]

As a microcontroller with a built-in conventional program ROM, 1
For example, as described in [Hitachi Microcomputer Data Book = 8-bit single chip, p. 49J, semiconductor manufacturers use fLOM in the integrated circuit manufacturing process.
A mask ROM in which a program is written is known. mask kLO
Although M is advantageous in that the memory layout is small, it has a problem in terms of confidentiality because the applied program created by the user is handed over to the semiconductor manufacturer.

As a microcomputer that solves the above-mentioned problem, a microcomputer with a built-in gPROM as described in the above-mentioned Data Book No. 823 has been developed. The microcontroller with built-in EPROM is an application developed by the user.

On the one hand, it has the advantage of security because the user can write the program himself, but on the other hand, it has the disadvantage that the memory area is three to four times larger than that of a mask ROM of the same capacity.

[Problem that the invention seeks to solve]

Although the above-mentioned conventional techniques have individual advantages, they also have drawbacks in terms of confidentiality and chip cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a program storage memory that minimizes chip cost, that is, chip area, and has excellent confidentiality.

[Means for solving problems]

The above purpose is to use manufacturer programmable mask ROM,
This is achieved by incorporating a user programmable PROM, dividing each block into a plurality of blocks, and arranging them alternately at consecutive addresses.

[Effect]

A series of completed processing programs are stored alternately in the mask ROM and PR4)M, so even if the program committed to the mask ROM is illegitimately decoded, the series of programs will be decoded unless it is related to the data written to the PROM. It is difficult and difficult to provide sensitive memory.

〔Example〕

Hereinafter, one embodiment of the F1 invention will be explained with reference to FIGS. 1 to 3.

FIG. 1 is a block diagram of a microcomputer.

Processor 2. on the same semiconductor substrate 1.几OM3、PRO
M4 is integrated, and each block has a common address a.
5. It is coupled to the common data line 6. Another 280
M is coupled to the external address line 7 and external data (i!8) so that it can be programmed from outside the semiconductor integrated circuit 1.

FIG. 2 shows the block configuration around the memory.

OM3 includes a ROM matrix 9, a readout circuit lO for reading ROM data, and 3 from the ROM matrix.
It is composed of a selection circuit 11 that selects words. PROM4 is PR, OM matrix 12.2280M readout circuit 13
, a PROM write circuit 14, and a selection circuit 15 that selects three words in the PROM memory. R.O.
The id and PROM selection circuits 11.15 select three words, La0M or PROM, based on the information from the address line 5, and output the data to the data line 6.

The selection circuits 11 and 15 alternately arrange the ROM area and PROM area at consecutive addresses as shown in the address map shown in FIG. This example has three steps (7).
Divide the ROM and IK bar (+4) PROM into 4 parts,
This is an example in which a total of 4 bytes are arranged in an address space.

Data writing to the mask ROM is performed by placing an order with a semiconductor manufacturer, and then a series of programming of the application program is completed by writing the PROM data at the user's hand.

According to this embodiment, since the application program is submitted to the semiconductor manufacturer in fragmented form, the entire content of the application program is not known, and a highly confidential semiconductor integrated circuit can be obtained. Also, since they are located in a continuous address space, mask ROM and PRO can be used during program/FA development.
Programs can be developed without being aware of M. Assuming that the area of PROM is four times larger than the area of R and OM of the same capacity, the above division realizes a highly confidential microcontroller with approximately 50% of the area compared to the case where the entire area is composed of PROM only. can.

〔Effect of the invention〕

According to the present invention, the problem of security when only a mask ROM is built-in and the problem of increase in chip size when only 280M is built-in are solved. Configure a microcomputer with memory. be able to.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and FIG.
The memory block diagram in the figure and FIG. 3 are explanatory diagrams of address assignment. 1... Semiconductor integrated circuit, 2... Processor, 3...
・ROM, 4...280M, 5...Common address line, 6...Common data line.

Claims (1)

[Claims] 1. In a semiconductor integrated circuit in which a ROM and a PROM are integrated on the same semiconductor substrate, one or both of the ROM and PROM is divided into a plurality of blocks, and the continuity of their addresses is broken, and the divided ROM blocks and A microcomputer configuration method characterized by placing PROM blocks alternately in a continuous address space.