| 摘要 |
<p>PURPOSE:To easily vary the capacity of a ROM by providing a means which discriminates the capacity of the connected ROM and an address decoding circuit which generates automatically a chip selecting signal suitable to the capacity of the ROM. CONSTITUTION:A microprocessor 1 reads the contents of the ROM 3 out of the initial address of a memory map 20 (or 30) and reads ROM capacity discrimination information. Consequently, the microprocessor 1 decides that the ROM 3 has the storage area of the memory map 20 (or 30) and applies a control signal (0 or 1) to the address decoding circuit 2 from an output port. Consequently, the address decoding circuit 2 switches ROMs 3 and 4 of the memory map 20 (or 30) according to the high-order 3-bit signal of an address bus.</p> |
