a method and circuit for receiving frame messages connected to one or more nodes , each controlled by a microcontroller , along a common transmission line of a multiplex communication system . the method includes the steps of : receiving the type and target bytes , and responsive thereto generating a first interrupt signal to the microcontroller at the node ; commanding the microcontroller , responsive to receiving the first interrupt signal , for qualifying the frame message by retrieving and matching one or more of the type and target bytes with corresponding bytes stored in programmable memory within the microcontroller , and responsive thereto generating a qualified signal ; and receiving data bytes from the frame message only responsive to receiving the qualified signal from the microcontroller .