A control unit, for controlling safety-critical applications, includes a microcomputer, a monitoring unit (check unit), and peripheral circuits (input/output), and in which, to improve the reliability of the error detection for such control units, and to expand the detection to additional error types, the monitoring unit includes a first apparatus, arrangement or structure for measuring the quiescent current of the microcomputer; at least one quiescent current handshake line for controlling the measurement of the quiescent current running between the first apparatus, arrangement or structure of the monitoring unit and the microcomputer; the monitoring unit including a second apparatus, arrangement or structure for applying a test data input signal to the microcomputer, for processing the test data input signal, and for comparing the corresponding test data output signal of the microcomputer to the corresponding test data output signal of the monitoring unit; and at least one test data signal transmission line running between the second apparatus, arrangement or structure of the monitoring unit and the microcomputer.
An ECU (100, 200) includes a monitoring circuit (2) having a counter (3) for selecting an assignment number (21) of an assignment signal (20), a serial communicating unit (4) for transmitting the assignment signal (20) of the assignment number (21) selected by the counter (3) and to and receiving an answer signal from a microcomputer (1). The ECU also includes a comparing/judging circuit (5) for comparing an answer number (11) with a correct answer number (30) and incrementing the assignment number (21) of the assignment signal selected by the counter (3) by one when both the answers match. This circuit (5) maintains the same assignment number (21) when the answers do not match. The microcomputer (1) performs the operation in conformity with the assignment number (21) of the assignment signal (20) received and transmits the operation result by using an answer signal (10).
