Patent ID: 7358628

Claim:
A circuit for monitoring the state of at least one switch, comprising: a monitoring circuit, coupled to a first terminal of a switch, the switch being one of a normally-open switch or a normally-closed switch, the monitoring circuit comprising: a normally-open detection circuit having a first input coupled to the first terminal of the switch and including a first sub-circuit for detecting when the switch, if configured as a normally-open switch, closes and the first input has transitioned to a high voltage value, and further including a second sub-circuit for detecting when the switch, if configured as a normally-open switch, closes and the first input has transitioned to a low voltage value, the normally-open detection circuit generating a first signal based on the detection; a normally-closed detection circuit having a second input also coupled to the first terminal of the switch and including a first sub-circuit for detecting when the switch, if configured as a normally-closed switch, opens and the second input has transitioned to a high voltage value, and further including a second sub-circuit for detecting when the switch, if configured as a normally-closed switch, closes and the second input has transitioned to a low voltage value, the normally-closed detection circuit generating a second signal based on the detection; and each detection circuit comprising a configuring circuit receiving a first control signal whose logic state selectively enables the normally-open detection circuit and disables the normally-closed detection circuit if the first control signal is in a first state or alternatively enables the normally-closed detection circuit and disables the normally-open detection circuit if the first control signal is in a second state, and further receiving a second control signal whose logic state selectively enables one or the other of the first and second sub-circuits based on whether input transition to the high and low voltage values, respectively, is to be detected.