| 摘要 |
PURPOSE:To simplify I/O control software, to reduce the number of signal lines and to improve an expanding capability at the increment of I/O by outputting an enable signal for each I/O in accordance with the counted value of a strobe signal. CONSTITUTION:Outputs from counting circuits 7a, 7b are inputted to decoders 9a, 9b through a counted value output line and initializing signals 10a, 10b and enable signals, 11a, 11b are outputted from the decoders, 9a, 9b. When an enable signal for controlling the final I/O is outputted, the counting circuits 7a, 7b are initialized by the initializing signals and similar operation is repeated again. Thus, the enable signals for the I/Os 2a-2c are outputted in accordance with the counted value of the strobe signals, so that an address bus for discriminating the I/Os 2a-2c is unnecessary. Thus, the I/O control software can be simplified, the number of signal lines can be reduced and the expanding property at the increment of the I/Os can be improved. |
