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Synchronous UART

Torben Frenzel
Prodigy 180 points


I need to implement a synchronous UART communication, where the clock is either applied externally (slave mode) or sent out on a pin (master mode). Or in other words: I want the UART protocol (Start/Stop bits, Parity bits) with the clocking mechanism from SPI.

Is this possible with either USART, USCI, eUSCI or USI modules?

Thanks

Torben Frenzel

  • 0
    Guru 227245 points

    Thsi is no problem. You can source the USCI module with an external clock.

    However, I think there must be a minimum factor of 2. The more, the better. Else receiving won't work. Remember, the UART is stillan asynchronous protocol, even if the clock is provided externally.

    So for 9600Bd, the external clock must be 19200Hz. or higher.

    If using and MSP with USI, you can program a 10 bit per byte transmission in SPI mode and manually add start and stop bits. The clock must then be injected through XT1 in bypass mode. Again, a minimum factor of two is required.

    If the baudrate is lwo enough, you can also implement it in software on every MSP.

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