Method and apparatus for protecting and monitoring the transmission of information between the central unit of a programmable controller and the sensors and/or the actuators of the controlled process

Claim 1

An input/output device for a programmable controller comprising a central unit connected to a bus having a determined number of data lines, said device comprising on at least one printed circuit board at least one input connecting element adapted to be connected a sensor so as to receive a state signal from said sensor, at least one output connecting element adopted to be connected an actuator so as to transmit a control signal to said actuator, input/output connecting elements which can be connected to said bus so as to receive, from the central unit, an output signal which must correspond to the control signal, and to transmit to said bus an input signal corresponding to the state signal, and at least first and second electronic channels which respectively connect said input/output connecting elements to said input connecting element and to said output connecting element, these first and second electronic channels forming two respective logic interfaces between said bus, said corresponding sensor and said corresponding actuator, wherein: i said first electronic channel comprises, a first galvanic decoupling means which is connected to said input connecting element so as to receive the state signal and to transmit to said input/output connecting elements a corresponding first internal logic signal; a second galvanic decoupling means connected to said input connecting element so as to receive the state signal and to generate a first external correlative logic signal corresponding to the said state signal; a first non concordance detection circuit connected to said first and second galvanic decoupling means for detecting non concordance between the said first internal logic signal and the said first external correlative signal, and for generating a first non concordance signal, and ii said second electronic channel comprises: a third galvanic decoupling means which is connected to said input/output connecting elements so as to receive said output signal and to transmit to said output connecting element a second internal signal corresponding to said control signal; a fourth galvanic decoupling means which is connected to the output connecting element and which comprises first detecting means for detecting said output signal and means for generating from this detection, a second external correlative signal representative of the control signal, and a second non concordance detection circuit connected to said third and fourth galvanic decoupling means for detecting non concordances between said second internal signal and said second external correlative signal, and for generating a second non concordance signal, said first and second non concordance signals being transmitted to the central unit through at least one first additional connecting element provided on the circuit board.