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MSP430G2553: USCI module during sleep

Chris Indo
Intellectual 300 points

Part Number: MSP430G2553

Hi all. 

We had an issue where the sleep current was high because the UCA0RXD pin was still connected to USCI when the device was in sleep -  the USCI was disabled.

We've corrected the issue by changing the Port Setting so that the pin is connected to P1DIR. (output low).   

However, we are curious about what is the pin actually connected to when the USCI is disabled - i.e. what is the actual transistor logic?

Does anyone know any details about that structure?

Thanks

Chris

  • 0
    TI__Mastermind 25455 points

    Hi Chris, Could you please check the Port Select register P1SEL and P1SEL2 before setting P1DIR and after setting P1DIR. I think it is related with Port function selection "General-purpose I/O" and "Primary module function".

  • 0 in reply to Xiaodong LI
    Intellectual 300 points

    Hi Xiaodong,

    Thank you for your fast responnse. We fixed the problem already by setting the P1SEL and P1SEL2 registers to the correct port function.   But does anyone knows the actual hardware of the USCI module?

    For example, when the port function is set to USCI module, 

    -  is the pin then connected to a pull-up or pull-down resistor?

    -  what is the capacitance?

    -  is it connected to internal ESD diodes?

    I will experiment and measure these things myself but I was just curious if anyone had any definitive knowledge of the internal hardware.

    etc.

    Thank You,

    Chris

  • 0 in reply to Chris Indo
    TI__Mastermind 25455 points
    Hi Chris
    This is the feedback on the USCI module I/O:
    - is the pin then connected to a pull-up or pull-down resistor?
    according to DS: www.ti.com/.../msp430g2553.pdf Page 42,Pull-up resistor or pull-down resistor depends on the value of P1OUT.1.
    according to UG: www.ti.com/.../slau144j.pdf Page 333, Digital I/O register table;
    The initial value of P1OUT is uncertain. Users can set the value of P1OUT at the beginning to determine the pull-up or pull-down resistor according to their needs.

    - what is the capacitance?
    according to DS：www.ti.com/.../msp430g2553.pdf Page 24
    The input capacitance value is 5pF as for a reference.

    - is it connected to internal ESD diodes?
    There is internal ESD cell in I/O pad.

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