| 摘要 |
<p>PURPOSE:To expand a memory space effectively, by assigning a part of plural memories to the same address space, and selecting only one memory by an output of a register to be turned on/off by the output of a processor. CONSTITUTION:An RAM64, an ROM166 and an ROM265 are connected to a CPU61 in common through an address bus 62 and a data bus 63. These memories have three logical modes; the RAM mode executes reading/writing in all addresses, the ROM1 and ROM2 modes, execute reading from the ROM1 or ROM2 and writing in the RAM in the first half addresses, and execute reading/writing from/in the RAM in the latter half addresses. In accordance with a register in a control part 67 to be turned on/off by an instruction outputted from the CPU61 through a control bus 68, the only mode in the memory specified by the same address is selected and the memory is accessed. If the ROM is connected freely atachably/detachably, another software can be executed.</p> |
