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MSP430F5528: MSP low-power microcontroller forum

Part Number: MSP430F5528

Hi,

Is it possible to use GPIOs in 5528 to implement 3 wire SPI (half duplex spi mode). 

  • Yes. F5528 supports 3-wire SPI mode and 4-wire SPI mode.

    If you look at the user's guide slau208, you can find the bot USCI_A and USCI_B support SPI interface. In the register description for UCAxCTL0.UCMODEx, you can see the SPI mode supported configuration: 

    bit 2-1: UCMODEx

    • U SCI mode. The UCMODEx bits select the synchronous mode when UCSYNC =1.
      00b = 3-pin SPI
      01b = 4-pin SPI with UCxSTE active high: Slave enabled when UCxSTE = 1
      10b = 4-pin SPI with UCxSTE active low: Slave enabled when UCxSTE = 0
      11b = I2C mode

    Thanks, 

    Lixin

  • Unfortunately, the terminology is somewhat muddled.

    Lixin has described 3-pin mode (sometimes "3-wire") which just means there is no /CS pin. The MSP430 USCI supports this.

    "3-wire" mode (sometimes "3-pin") means that MISO and MOSI use the same physical wire, and master/slave alternately drive that wire based on some higher-level protocol. The MSP430 USCI doesn't support this -- you need to do it explicitly, by switching the pins (PSEL) at the right times.

  • Hi Lixin / Bruce,

    Thanks for the reply. 

    Good to know that its possible to use PSEL and implement the protocol till the timing parameters are satisfied.