If the receiver times its samples based on its own clock, then there will be a problem if the transmitter’s and receiver’s clocks are not precisely aligned. If there is a drift of 1% (the receiver’s clock is 1% faster or slower than the transmitter’s clock), then the first sampling will be 0.01 of a bit time away from the center of the bit (center of bit is from beginning andend of bit).After 50 or more samples, the receiver may be in error because it is sampling in the wrong bit time For smaller timing differences, the error would occur later, but eventually the receiver will be out of step with the transmitter if the transmitter sends a sufficiently long stream of bits and if no steps are taken to synchronize the transmitter and receiver.
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