| 摘要 |
PURPOSE:To eliminate mis-diagnosis by stopping the access of a processor in a display controller to a memory while a central processing unit diagnoses the display controller. CONSTITUTION:In diagnosing the display controller 20';, after the central control ler 30 stores in-diagnosis information DD in a register 11 is the display controller 20', the controller 30 gives a mask disable interruption signal NMI to a proces sor 4 in the display controller 20'. The processor 4 receiving the signal supervises the register 11 at each period setting initially a timer circuit 10 and when the processor 4 detects that the said information DD is stored, the timer circuit 10 is set initially and the access or other processing to a transmis sion signal memory 8 and a reception signal memory 9 are stopped at all. Thus, even when the central controller 30 writes diagnostic information DI to diagnose the memory 8 nor 9, the possibility of the processor 4 changing the DI is precluded. |
