| 摘要 |
PURPOSE:To realize power saving which does not run away even in case when an impulsive noise is generated on a bus, by cutting off a power source of a PROM after a bus of a microprocessor becomes high impedance exactly. CONSTITUTION:A program for operating a microprocessor MPU, and a system parameter are written in a programmable read-only memory PROM-1 and a PROM-2, respectively. When an interruption IRQ(1) is received, the microprocessor MPU outputs a PROM power-down instruction. After this instruction is executed, a bus is set to a high impedance state. In this case, when a power source of the PROM-2 is cut off, an impulsive noise is generated, and there is the possibility that the microprocessor MPU runs away, therefore, until the microprocessor MPU ends an execution of a wait-for IRQ(2), the execution of the power-down instruction of the read-only memory PROM-2 is delayed. |
