SAFETY OUTPUT CONTROL FOR A DATA PROCESSING SYSTEM EMITTING BINARY SIGNALS

摘要

A safety output unit for a data processing installation which in use supplies binary signals, the safety output unit being for supplying an output amplifier comprising an output transformer having a secondary winding which in use supplies a load with fail-safe signals through a rectifier arrangement. The unit comprises inputs for coupling to a pair of data lines which in use carry like binary signals from two micro-computers which are synchronously controlled by a common timing current supply. Two first triggering elements are coupled to receive data via respective ones of the inputs and have outputs connected to reset inputs of two respective second triggering elements of the safety output unit. The two second triggering elements have timing inputs available to receive synchronous timing pulses from the timing current supply and the two first triggering elements comprise reset inputs available for connection to the timing current supply to receive therefrom a normal setting signal. There is connected to a negated output of one second triggering element and to an output of the other second triggering element an exclusive-OR monitoring element which can be read in dependence upon test pulses from the timing current supply and which is arranged to output the test pulses from the the case of static exclusive-OR signals and in the case of dynamic exclusiveOR signals for maintaining the timing current supply, at least one of the two second triggering elements being available for connection to an output amplifier which is to be supplied by the safety output unit.