| 摘要 |
<p>PURPOSE:To use effectively an external terminal by the external input or output terminal of a transfer circuit to the external terminal of a parallel input-output port and then by allowing the parallel input-output port and data transfer circuit to share the same external terminal. CONSTITUTION:In mode 1, external terminals E,F,G,H, and I are used for input and output data having passed through parallel input-output port A and in mode 2, they are used for series input-output insterruption request part B, counter interruption request part C and external inerruption request part D. By making output control signal S17 of request part B inactive, the output of driver 10 is held at level ''H'' and the same effect as the separation of request part B from terminal G is caused to send or receive correctly output S3 or input S8 to or from port A. When output control signal S24 is made inactive by request part C to hold the output of driver 13 at level ''H'', the same effect as the separation of request part C from terminal F can be obtained, so that output S1 or input S6 will correctly be sent or received to and from port A. Supplying port A with an output pulling up external terminals allows request parts B-D inmode 2 to operate normally.</p> |
