An electronic engine control system that uses a microcomputer has been developed. It combines four control systems - fuel injection, ignition timing, EGR and idle speed control - utilizing the engine speed and intake air quantity for its main parameters.
The control circuit is composed of an 8-bit microcomputer combining an 8k byte ROM, RAM, a custom designed input/output LSI, and two hybrid integrated circuits, one has voltage regulators and another has input/output interface circuits.
The control program consists of a main program, a fail-safe program for noise protection and a check program for diagnostic functions.
The main program uses interrupt techniques to control effectively the four items by one microcomputer. The interrupt requests occur from crankshaft position signal and interval timer signals.