| 摘要 |
PROBLEM TO BE SOLVED: To accurately read data from a ROM by inhibiting the access of a CPU to a memory until a prescribed time elapses when the memory is shifted from a standby state to an active state. SOLUTION: When the CPU 39 is set to the module of accessing the ROM 41, control circuits 21-24 output an activation command for instructing the activation of active voltage supply circuits 25-28 so as to turn the ROM 41 to the active state and to make the CPU 39 able to access the ROM 41. In this case, this voltage drop circuit is constituted so as to inhibit access of the CPU 39 to the ROM 41 until a prescribed time elapses when the ROM 41 is shifted from the standby state to the active state. Thus, the failure that the CPU 39 accesses the ROM 41 when a drop voltage outputted from the active voltage supply circuits 25-28 is unstable is dissolved.
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