| 摘要 |
PROBLEM TO BE SOLVED: To make increasable the ROM operation margin by lengthening a ROMTr forming period to solve such a problem that read-out in ROM operation may be failed and ROM operation margin may not be given during a ROMTr forming period, namely margin is not given at a 'High' level of a pre-charge signal in a ROM driving circuit. SOLUTION: The number of stages of a N-MOS transistor 21 is made more than the number of stages of a N-MOSTy 31 of a MainROM 13. Thereby after pre-charge of the MainROM 13 is finished, pre-charge of the N-MOSTr 21 of the gate circuit 14 is finished later (pre-charge signal 43 is at 'High' level), and thus, the ROM operation margin is increased by lengthening the ROMTr forming period.
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