| 摘要 |
A counter circuit comprises a signal detector for providing an up/down indication signal and a count clock signal according to an up/down signal and a reference clock signal. A n-bit counter for providing up/down count data of "n" bits according to the up/down indication signal and count clock signal. A counting direction detector provides a counting direction signal according to the up/down indication signal and reference clock signal. This counter circuit itself determines whether it is counting up or counting down, by hardware, and thus can instantaneously respond to a direction identification request from a central processing unit.
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