| 摘要 |
PURPOSE:To prevent a memory area for a microprogram muP for control from being reduced owing to a muP for diagnosis by providing a ROM stored with the control muP and a ROM stored with the diagnostic muP together with a memory changeover switch. CONSTITUTION:The 1st ROM3 is stored with the control muP and the 2nd ROM4 is stored with the diagnostic muP. A muP controller 1 sends out a muP memory address through an address signal line 2 to read instructions to be executed out of the ROM3 or ROM4 through a data signal line 6, and then executes them. When normal control is performed, the bus driver 8 of the ROM3 is enabled with the switch 7 and the control muP is read out and executed. When the switch 7 is set to the opposite side, the ROM4 is selected and the diagnostic muP is read out and executed. Thus, the switch 7 is operated to read the contents of the ROMs 3 and 4 and execute instructions, so that the effective memory space is expanded and used.
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