Initialization processing system of in-car microcomputer

摘要

An external interrupt port is installed for writing a password into a random access memory by monitoring low voltage with an interrupt when a battery is turned off and on instantaneously and performing ignition off processing. During Random access memory initialization the system disables an external interrupt and initializes output of ports containing the external interrupt port when an ignition switch is turned on, next makes a password check just after initializing output of the ports, then enables an external interrupt and executes initialization.