Обязательно нужно, а то получится как у блэкфина («Телесистемы»: Конференция «Микроконтроллеры и их применение»)

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Телесистемы | Электроника | Конференция «Микроконтроллеры и их применение»

Обязательно нужно, а то получится как у блэкфина

Отправлено BTW 19 июня 2007 г. 11:26
В ответ на: Ну это не вопрос, можно такое заваять. отправлено SM 19 июня 2007 г. 11:20

UART Receiver is Less Robust Against Baudrate Differences in Certain Conditions:
DESCRIPTION:
In asynchronous communications, transmitter and receiver bit clocks can differ to a certain percentage of the nominal value. The exact
amount is dependent upon the configuration of the word to be transmitted and other external factors such as signal quality.
For the Blackfin UART receiver, the tolerance is different when its bit-clock is slower or faster than the sender's clock. The Blackfin UART
receiver will tolerate differences well when the transmitting side (sender) is operating at slightly lower bit rates. If, however, the sender is
operating at slightly higher bit rates than the Blackfin receiver, the communication may fail for back-to-back transfers (i.e. no gaps
between the words).
The reason for this is that the receiver, as per the standard implementation, samples the stop-bit, like any other bit, 16 times before it is
ready to detect a new start bit condition. Since the decision of whether a stop-bit has been detected is done after the 9th sample, the
receiver should immediately be ready for the next word if a stop-bit is detected. Instead, the Blackfin receiver will take the remaining 7
samples as well.
The effect of this is that the sampling error may accumulate for the kind of data transfers described above.
The anomaly has no effect on single transfers or transfers with gaps between the words, as the sampling error will not accumulate.

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Интересно, остались ли ещё девственные грабли, на которые никто не наступал? — vmp (19.06.2007 11:37:48 87.245.155.196, пустое)