| 摘要 |
A digital electronic circuit device includes a CPU provided with multiplexed address/data terminals and exclusive address terminals, an expansion port provided with data terminals and exclusive address terminals, a multiplexed address/data bus connecting the multiplexed address/data terminals with the data terminals and an address bus connecting the address terminals of the CPU with the address terminals of the expansion port. If a program for the CPU is likely to contain many bugs, a detachable external ROM for storing the program and an address latch are connected with the multiplexed address/data bus. The address latch receives address signals from the multiplexed address/data bus, temporarily stores these signals and addresses the external ROM.
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