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USCI input clock

Prad
Expert 1125 points
Other Parts Discussed in Thread: MSP430F5419

 

Hi,

 

This may be a basic question about MSP430F5xx USCI,

when using USCI in UART Mode, there is an option for USCI clock source called UCLK.

Please let me know, is it possible to use an external clock connected to 

the clock input(UCA0CLK) in UART mode and which exact pin on MSP430F5419 could be used for this.

 

Thankyou.

 

  • 0
    Guru 227245 points

    The pinout in the 54xx device datasheet lists which pin is for what. In case of USCI A0, the clock input for UCLK (uart mode) is ACA0CLK, which is connected to pin 33 (P3.0). The pin needs to be configured as input (default) and selected (P3SEL|=1), and for UCB0 the SPI 4-pin modes cannot be used (the use as CLK has precedence and will revert the SPI to 3-pin mode automatically)

     

  • 0 in reply to Jens-Michael Gross
    Expert 1125 points

    Hi Jens,

     

    Thankyou,

     

    I was confused that, unlike the older 2xx or 4xx series, 

    in the datasheet of F5419, the pin P3.0(UCA0CLK) 

    has a description saying "Clock signal input - USCI_A0 SPI slave mode",

    but for example the same pin for external USCI CLK in F2274 is described as "USCI_A0 clock input".

     

    Regards,

  • 0 in reply to Prad
    Guru 227245 points

    The UCBxCLK pin is also the clock input pin for the I2C slave mode, so it is an educated guess that it will be the clock input for external clock UART mode for UCAx too.

    I didn't ever use an external clock anyway (neither for SPI nor for I2C or UART), so I cannot be 100% sure. But then, which other pin could it be?

    The USCI modules, while widely identical with the 54xx USCIs, have undegone some minor redesign to be more modular. I think this has not only affected the interrupt vectors (one per module, shared for RX and TX) and IE/IFG registers but also the pin designations.

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