INHERENT FAIL SAFE ENABLING CONTROL AND COMMAND UNIT WITH TWO OUT OF TWO ARCHITECTURE

摘要

Inherent fail safe enabling control and command unit with two out of two architecture comprising a logic processing unit (2) with two processing channels executing independently and in parallel the same processing program on same input data and generating two output signals (INPUT_DATI_Q_A and INPUT_DATI_Q_N_B) to a voter unit (1) comprising a signal comparator (120) for determining the congruence of the two output signals and a signal generator (140, 150) for generating a vital enable signal only as long as the two signals (INPUT_DATA_Q_A and INPUT_DATA_Q_N_B) are congruent. The voter unit (1) has timer means (140; 141) for measuring the frequency of the incongruence events in the comparison of the two output signals and for disabling the vital enable signal only for a predetermined and limited time period when the incongruence events are one isolated event or the frequency of the said incongruence is lower than a certain threshold.