| 摘要 |
<p>PURPOSE:To make reliability high, to reduce cost, and to change and correct a program in an emergency by accessing a PROM or a mask ROM by an instruction means. CONSTITUTION:When one module in the program of the system becomes defec tive, and it has to be corrected in an emergency, first, a new corrected program module is written into a PROM 3 and packaged in a part of a PROM 3, a mode changeover switch 5 is switched to a defective module 'present' side. The value of the mode changeover switch 5 right after restarting is read out by a main program, and when it is 'present', an area for designating module name of the defective program inside of the PROM 3 is read out, and after this, the part of the defective module of the ROM 2 is not executed, but the replacement module inside of the PROM 3 is used. Thus, the system with high reliability, low cost, and a program which can be changed in an emergency, can be obtained.</p> |
