| 摘要 |
PURPOSE:To switch easily output instructions by using a multiplexer which defines plural instructions as an input and a decoder which delivers an output switching instruction and selecting an instruction to be delivered by the decoder. CONSTITUTION:Two inputs of a multiplexer 11 are connected to outputs SIGMAE and SIGMAO of a parity check circuit 16, and the output of an FF13 is connected to a selection input. When a power supply is turned on, a reset pulse is delivered from a power-on reset circuit 15. Thus the selection input of the multiplexer 11 is set at a low level, and a parity is checked by the SIGMAE. When it is desired to change the parity at the SIGMAO, the output 1 of a decoder 12 is set at a low level. Then the output 2 of the decoder 12 is set at a low level when it is desired to change the parity into the SIGMAE. In such a way, a parity error display circuit 17 can switch the connection to the SIGMAO to the connection to the SIGMAE for the circuit 16. In other words, switching of output instructions is facilitated by selecting an instruction to be delivered from the multiplexer 11 by the decoder 12. |
