| 摘要 |
PURPOSE:To enable a host CPU to check periodically input signals and to confirm its working by utilizing a timer to inform an interruption of a long fixed cycle in addition to information of the interruption for the change detected by program control. CONSTITUTION:A digital input signal is sent to an input buffer 5 and a sampling buffer 6 through an input gate 4 and sampled periodically by the program control of an interruption program control part 7 to be compared with the previous sampling data for detection of change. When a change is detected, an interruption is informed to a host CPU 9. Thus the buffer 5 is sampled. In addition, a timer, etc. is used to give information on the interruption to the CPU 9 periodically and in a fixed cycle longer than the sampling cycle. In such a way, a collation is possible between the input signal recognized by a digital input/output controller A and that recognized by the CPU 9. Furthermore, the difference between both input signals can also be recovered. |
