Patent ID: 6715051
Filing Date: 2004-03-30
Classification: G06F

Abstract:
A program modification device for executing modified programs in place of programs unable to be modified as-is because of being fixedly recorded in an instruction ROM or the like, comprising:a CPU core unit; a memory for modification target program data for storing modification target program data corresponding to modification source program data before said CPU core unit starts program execution; a modifying address storage table for storing a necessary number of pairs of addresses of such modification source program data and addresses of such modification target program data before said CPU core unit starts program execution; a modifying address register for storing the addresses of such modification source program data and addresses of such modification target program data before said CPU core unit starts to execute such modification source program data; an execution unit located in said CPU core unit for loading into said memory for modification target program data addresses of such modification source program data and the addresses of such modification target program data from said modifying address storage table to predetermined positions in said modifying address register in accordance with contents of load modification instructions, when said execution unit detects such load modification instructions in a program, based on address information stored in said modifying address register; a program monitor unit for detecting agreement between an address of program data to be executed by said CPU core unit and an address of modification source program data in said modifying address register, with reference to said modifying address register, before execution of modification source program data corresponding to such modification source program address; and an acquired instruction switch unit for performing replacement of necessary program data and addresses in order to make said execution unit in said CPU core unit read from said memory for modification target program data the program data at a modification target address corresponding to the program data at a modification source address stored in said modifying address register, instead of the program data at such modification source address, when said program monitor unit detects agreement between both addresses.