| 摘要 |
PURPOSE:To evade a runaway state, by providing a reset signal line, and applying reset on and initializing a CPU when the CPU reads an area where no program is stored at the time of executing the program. CONSTITUTION:When an RD signal is outputted from the CPU1 to a memory 2 via a read signal line 5, the content (n+1 bits) of the address of the memory 2 decided by an address signal on an address bus 3 at that time is read in the CPU1 via a data bus 4. And it is decided whether the address is valid or invalid by using the value of a prescribed one bit (reset bit) connected to a reset signal line 6. In other words, when the reset bit is set at 1 (when the address is present outside a programs area and invalid), the reset is applied on the CPU1, then, the CPU1 is initialized. In such a way, it is possible to block the continuous runaway of the program by reading an invalid data as an instruction by the CPU1. |
