Engine control microprocessor start-up circuit

Claim 1

In an internal combustion engine powered automotive vehicle having an electromechanically operated engine throttle mechanism of the type wherein an input means comprising a transducer which is operated by the vehicle's driver delivers an input command signal to a microprocessor-based control, the microprocessor delivers a throttle command signal to an output means comprising an electromechanical prime mover which operates the throttle mechanism, the microprocessor receives one or more other input signals from other input means, the microprocessor is programmed to develop the throttle command signal in accordance with an algorithm which utilizes information derived from said input command signal and said one or more other input signals, and the microprocessor comprises internal circuitry which is connected with external circuitry that includes the parallel circuit combination of a crystal and a starting resistance configured to initiate and sustain electrical oscillation of the combined circuitries and cause the generation of an internal clock signal within the microprocessor at a frequency related to said electrical oscillation, the improvement which comprises said starting resistance comprising two individual resistance means connected in parallel circuit relationship with each other and directly connected to said microprocessor internal circuitry, said two individual resistance means having respective resistance values which in their parallel circuit relationship connection are effective to cause the initiation of said electrical oscillation in the combined circuitries and which are also individually effective to cause the initiation of said electrical oscillation in the combined circuitries so that in the event that either one of said individual resistance means experiences an open circuit fault, said oscillation can nonetheless be initiated and sustained by the other of said individual resistance means.