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Method of controlling data writing into on-board microcomputer

  • US 5,835,706 A
  • Filed: 12/24/1996
  • Issued: 11/10/1998
  • Est. Priority Date: 01/17/1996
  • Status: Expired due to Fees
First Claim
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1. A method of controlling the writing of data, comprising the steps of:

  • providing a user board having a user circuit including a serial interface function block and a malfunction monitoring device, an on-board microcomputer including a flash memory which stores a control main program and an on-board writing program memory which stores an on-board writing program and connected to said user circuit through serial interfaces, a reset circuit for generating a reset signal in response to an output signal from said malfunction monitoring device, a first OR gate for ORing said reset signal from said reset circuit and a reset signal supplied from an on-board writing host for rewriting data stored in said flash memory, and a second OR gate for ORing an output signal from said first OR gate and a detected signal indicative of an on-board writing mode from said on-board writing host to reset the user circuit;

    supplying a high-voltage signal having a voltage higher than a power supply voltage from said on-board writing host to energize said on-board writing program memory to thereby indicate a start of the on-board writing mode;

    transmitting data to be written into said flash memory from said on-board writing host to said on-board microcomputer; and

    inhibiting operation of at least a part of said user circuit as long as said detected signal indicates the on-board writing mode.

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