Diagnostic check system for digital signal circuit

摘要

A diagnostic check system for a digital signal circuit, in which, in a state where a plurality of digital signals are being sent out from a processor such as a microcomputer through an interface and photo-coupling elements to a controlled apparatus, the processor periodically processes all the digital signals to simultaneously cause them to be the same signal mode "1" or "0" for a period of time that is too short for the controlled apparatus to respond to the change in the levels of the digital signals, and the processor also detects whether the modes of all the signals transferred from the photo-coupling elements to the controlled apparatus for the short period of time are coincident or not.