| 摘要 |
PURPOSE:To check the capacities of packaged RAMs correctly even when the RAMs are not fully decoded by accessing data for checking in a specific address. CONSTITUTION:Addresses of an RAM 12 are assigned according to a memory map and a CPU 12 writes write data '15' on an address 0 of the RAM 12, reads the address 0, and compares both the write and read data with each other to know the presence of the RAM 12. Similarly, the presence of an RAM 13 is also known. Then, '14' is written in an address 10,000H and read out; and the address is increased by 10,000H and data is decreased by '1'. Then, an address 20,000H is accessed, but the RAMs 12 and 13 are not mapped, so data '13' is not read out, so that the CPU 10 knows the capacities of the RAMs 12 and 13.
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