| 摘要 |
PURPOSE: An option control circuit is provided to reduce a hardware size and simplify design by integrating a program ROM and an option ROM CONSTITUTION: An option control circuit comprises an option address generator, a multiplexer, a program memory and a latch. The option address generator(202) drives by an option lead signal(OR) and outputs an option address. An external address, an option address and an option lead signal (OR) as a choice signal are input to the multiplexer(204) through the address bus. Then, an address is inputted to the program memory(206) through the multiplexer (204) and a system control program containing option data is stored. The data output from the program memory(206) and an option lead signal(OR) as a clock signal are inputted to the latch(208) through the data bus.
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