| 摘要 |
PURPOSE:To simply change a control program and the control data used for a microcomputer with use of an external memory by making use of an input/ output terminal of the microprocessor. CONSTITUTION:When the desired data to be written into an EP-ROM 3 via a microprocessor is supplied, the address data for writing is delivered from an input/output port. This address data is partly given to the ROM 3. While the rest of said address data is latched by a latch circuit 5 and given to the ROM 3 so that an address is designated. The data are also outputted through the input/output port and then stored in a desired address of the ROM 3 after the ROM 3 is set under a writable state. When this stored data is used by the microprocessor, an address is designated in the same procedure as that of a writing case. Then the ROM 3 is set in a read mode and the read-out data are fetched by the microprocessor via the input/output port.
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