| 摘要 |
PURPOSE:To prevent the locking condition of a computer system and the run-away by providing a means to output a detecting signal when the address of a program counter comes to be the address in which an access is prohibited. CONSTITUTION:A program counter 1 outputs an output ADDR corresponding to the address while the address is stepped by the output of an AND circuit 2. When an address comparing circuit 3, when the output ADDR of the counter 1 arrives at the head address of an access prohibiting area, detects this, and outputs a detecting signal CMP. As such a result, the output of an inverter 4 comes to be 0, a control signal PCIN is shifted to a high level and even then, the output signal of the AND circuit 2 is in the condition of 0 and the address of the counter 1 will not step. When the signal CMP comes to be 1, a gate circuit group 7 is turned on through an AND circuit 5, a computer system is initialized by a presetting register 6 and the locking condition and the run-away can be prevented. |
