| 摘要 |
PURPOSE:To omit a large capacity ROM by connecting a diagnosis program to a control program so that the address spaces of both programs have no overlap when viewed from the CPU side and that the accesses are possible to both programs with different address values. CONSTITUTION:When a CPU 25 delivers successively the addresses for access to addresses 0001-0002, a jump instruction production program read out from a ROM 30 is executed. Then the CPU 25 gives an access to an address 'a3a2a1a0' of a jumping destination. This address value is set at 4,000, for example, out of a range of addresses 0000-3FFF used for access to a control program stored in a ROM 26. When the CPU 25 delivers the address values of 4,000-4FFF, the addresses 1,000-1FFF of the ROM 30 receive accesses. For this purpose, the address output terminals A0-A15 of the CPU 25 are connected to the address input terminals B0-B12 of the ROM 30 so that the bit weighting is carried out in different ways. In such a way, a control program and a diagnosis program are connected to each other with no overlap. Thus the capacity of the ROM 30 can be reduced. |
