MICROCOMPUTER AND ITS PROGRAM CORRECTING METHOD

摘要

PROBLEM TO BE SOLVED: To correct a bug generated in a program stored in a ROM built in an one-time PROM microcomputer (OTP.MCU) and to reuse the OTP.MCU having a detect. SOLUTION: An extra bit b8 is added to an instruction code and stored in an extra bit area 26 formed in an one-time PROM 16. When a bug is detected in the instruction code, the bit b8 is inverted to '0' and the corrected code is written in the leading address A1 of a space area 24. A 1st judging circuit 30 reads out the bit b8, and when b8='1', a 1st gate 28 reads out the instruction code. In the case of b8='0', a 1st jump instruction generating circuit generates a 'JUMP A1' instruction and jumps the instruction code to the leading address A1 of the space area 24.