Circuit for cancelling the resetting of a microprocessor

摘要

A semiconductor element handling the resetting is switched by the charge of a capacitor (3). This charge is periodically changed after a limit value has been reached and, as a result, the reset signal (R) of a particular period is generated in the semiconductor element. After the period has elapsed, the reset signal (R) is suppressed by a disturbance voltage opposing the charging-up of the capacitor (3). The circuit comprises a disturbance-signal circuit (1) and an oscillator circuit (2) containing the capacitor (3). The disturbance-signal circuit (1) is activated by squarewave pulses (UE) generated by the microprocessor and outputs differentiated and rectified disturbance voltages to the oscillator circuit (2). The oscillator circuit contains a multivibrator circuit, activated by the capacitor (3) and containing a comparator (7). The threshold voltage (US) for the non-inverting (+) input of the comparator (7) is generated from the supply voltage (VCC) by means of a voltage divider. The oscillating frequency and the period of the reset signal (R) is determined by the time constant of the capacitor (3) together with the resistance (13) and the threshold voltage of (US). <IMAGE>