| 摘要 |
PURPOSE:To prevent the user data from being broken down at the time when the CPU runs away due to instantaneous disconnection of the power source supply by detecting the runaway of the CPU by an identification code in a volatile memory. CONSTITUTION:User data is stored in an E<2>PROM 30, a ROM 20 and the E<2> PROM 30 are nonvolatile memories, and even if the power source supply from a power source terminal Vcc is used up, stored data is not lost. Also, a RAM 40 is a volatile memory whose stored data is lost, when the power source supply from the power source terminal Vcc is gone. In such a state, when such as abnormal state as instantaneous disconnection of the power source supply is generated, data in the RAM 40 is broken and a CPU 10 runs away, and in this case, an identification code is also broken, and an erroneous write operation is suspended. In such a way, the rewriting of user data in the E<2>PROM 30 in the case the CPU 10 runs away due to instantaneous disconnection of the power source supply is prevented. |
