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Thread: Use of RXEDGIE on Uarts 0,1,2

  1. #1
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    Use of RXEDGIE on Uarts 0,1,2

    Paul, or any other Guru:
    I was reading the Uart section of the K20 Manual today and came across an interesting little tidbit on page 1208 and 1209, concerning an obscure little know interrupt on the K20 called RXEDGIE which says:
    RxD Input Active Edge Interrupt Enable:
    RXEDGIE
    Enables the receive input active edge, RXEDGIF, to generate interrupt requests.
    0 Hardware interrupts from RXEDGIF disabled using polling.
    1 RXEDGIF interrupt request enabled.

    And on page 1216 concerning RXEDGIF:
    RxD Pin Active Edge Interrupt Flag
    RXEDGIF is set when an active edge occurs on the RxD pin. The active edge is falling if RXINV = 0, and
    rising if RXINV=1. RXEDGIF is cleared by writing a 1 to it. See for additional details. RXEDGIF description NOTE: The active edge is detected only in two wire mode and on receiving data coming from the RxD
    pin.
    0 No active edge on the receive pin has occurred.
    1 An active edge on the receive pin has occurred.

    I would like to use this interrupt, however when I went looking for the ability to set the Enable bit "RXEDGIE" I found that this definition is missing. This bit is at bit 6 of the UART_BDH field and I was wondering why its missing?
    Is this some obscure use of the Uarts that has been deleted or is it just an oversight?

    Thanks,
    Ed

  2. #2
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    I have not looked into the UART libraries lately, being deep into a big project at work. If the definition is not present in the code, it's probably just an oversight.

    My project uses RXEDGIF (though not as an interrupt source) so I know that it works well.

    ... Your question reminds me to try something. I wonder whether it's possible to get an interrupt using RXEDGIE with the receiver *disabled*...

    Answer: The receiver needs to be enabled for RXEDGIF to be detected.
    Last edited by LenSamuelson; 02-23-2018 at 02:11 PM.

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