| 摘要 |
PURPOSE:To change instructions in a ROM by generating a pseudo jump instruction externally and switching the instruction sequence from a program area to be changed on the ROM to a correction program area on a RAM. CONSTITUTION:A processor 1 sets the head address of a part to be corrected in the program on a ROM 2 to a change address set register 6. Meanwhile, the address of the correction program stored in a RAM 3 and the jump instruction code are set to a correction program address register 7. If the address issued from the processor 1 in an instruction fetch cycle coincides with the change address set to the register 6, the ROM 2 is disconnected and the jump instruction is issued, and the address set to the register 7 is fetched into a program counter 9 to transfer the control of instruction execution from the ROM 2 to the RAM 3. Thus, instructions in the ROM are changed.
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