| 摘要 |
PURPOSE:To extend a ROM area by dividing address multiplex areas of a ROM and a RAM and switching each divided area to a ROM area or a RAM area to use it. CONSTITUTION:If the signal on a memory controlling signal line 103 means extension of the ROM area in case of memory access, a memory control circuit 14 validates a ROM from address 0 to address B on a memory map by the signal on a ROM select signal line 104 and validates a RAM from address B to address C by the signal on a RAM select signal line 105. If the signal on the memory switching signal line 103 means reduction of the ROM area, the memory control circuit 14 validates the ROM from address 0 to address A on the memory map by the signal on the ROM select signal line 104 and validates the RAM from address A to address C by the signal on the RAM select signal line 105.
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