| 摘要 |
PURPOSE:To prevent a program after IPL from being destroyed when executed by allowing writing to a program area from the generation of an IPL(Initial Program Load) request to the end of the loading of the program. CONSTITUTION:A microprocessor 1 starts processing following the IPL program stored in a ROM 2 in response to the IPL request, sends a write permission instruction for permitting writing to the program area of a RAM 5 to an IPL control circuit 11, and then loads the program which is stored in an external memory device in the program area of the RAM 5. Then the program is loaded in the program area of the RAM 5. Then when the loading of the program ends, the microprocessor 1 sends a write inhibition instruction which instructs the writing to the program area to the IPL control circuit 11. Consequently, the program which is loaded initially is prevented from being destroyed when executed.
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