昨天看AVR-lib的资料上这样说：
Why are (many) interrupt flags cleared by writing a logical 1?
........
The solution is simple: writing a logical 1 to it requires only a single OUT instruction,
and it is clear that only this single interrupt request bit will be cleared. There is no need
to perform a read-modify-write cycle (like, an SBI instruction), since all bits in these
control registers are interrupt bits, and writing a logical 0 to the remaining bits (as it
is done by the simple OUT instruction) will not alter them, so there is no risk of any
race condition that might accidentally clear another interrupt request bit. So instead of
writing
TIFR |= _BV(TOV0); /* wrong! */
simply use
TIFR = _BV(TOV0);
用TIFR |= _BV(TOV0);是不是真的错???我一直这样用的!!! |
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