| 摘要 |
<p>PURPOSE:To constitute a key data input part with a TTL circuit without providing a special LSI circuit by supplying a clock for synchronism at the time, when key data is transferred from the reception side, namely, the input control part side, to a keyboard. CONSTITUTION:An input control part 12 includes a serial-parallel converting circuit and is provided between a CPU 10 and a keyboard 11. The control part 12 receives key data through a signal line 15 in one-bit serial. The keyboard 11 receives a clock for key data transfer through a clock signal line and outputs key data synchronously with this clock. The clock is generated by a clock generating circuit 13 and is transferred to a clock signal line 17 through a gate circuit 14. When key data is inputted to the CPU 10, the CPU 10 sends a clock supply start signal 19 to the circuit 14 to permit the next key data input. Thus, the interface between the keyboard and the CPU is possible with an input circuit of a TTL mechanism without a special LSI circuit.</p> |
