Patent ID: 6341239
Filing Date: 2002-01-22
Classification: G05B

Abstract:
An electronic control unit connectable to an external unit, comprising:a microcomputer that executes a control program composed of data stored in a rewritable nonvolatile memory storage contents of which can electrically be rewritten, and executes a control process for controlling a control object; and monitor circuit that monitors whether an execution state of the control program by the microcomputer is normal or abnormal, wherein the microcomputer is constructed to execute a rewrite process for updating to write a rewrite data transmitted from the external unit into the rewritable nonvolatile memory, when the execution state of the control program is determined to be abnormal by the monitor circuit; the microcomputer is constructed to execute, immediately after starting an operation from a reset state, a starting program stored in a non-rewrite-object nonvolatile memory thereby determining a level of a mode determining binary signal inputted to a self specific input terminal, and in accordance with the level of the mode determining binary signal, switch a self operation mode into either one of a normal mode to execute the control program stored in the rewritable nonvolatile memory and a rewrite mode to execute the rewrite process; and the monitor circuit is constructed to output a reset pulse for resetting the microcomputer to a reset terminal of the microcomputer, and outputs the mode determining binary signal of a level corresponding to the rewrite mode to the specific input terminal of the microcomputer, when determining the execution state of the control program by the microcomputer as being abnormal.