| 摘要 |
PURPOSE: A RAM access device having a function of access time adjustment optionally is provided to exclude the probability of malfunction due to the uniform reduction of instruction proceeding time by dualizing the system formation mode of a RAM access device. CONSTITUTION: The device comprises an expanded RAM access instruction converting table(110), a first selecting unit, a second selecting unit, a system configuration flag register(180), and a logic circuit. An instruction for accessing an expanded RAM is mapped as an instruction for accessing an internal RAM by a code mapping rule, and is stored in the expanded RAM access instruction converting table. The expanded RAM access instruction converting table checks if a fetched instruction is an expanded RAM access instruction. If the fetched instruction is an expanded RAM access memory, the first selecting unit outputs the converted instruction output from the expanded RAM access instruction converting table to the instruction register. The second selecting unit selectively outputs an internal RAM(170) address or an expanded RAM(160) address to the RAM.
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