Category

Functional

Function

SPI Slave Transmit with clock phase select = 1

Description

In SPI slave mode with clock phase select set to 1 (UCAxCTLW0.UCCKPH=1), after the first TX byte, all following bytes are shifted by one bit with shift direction dependent on UCMSB. This is due to the internal shift register getting pre-loaded asynchronously when writing to the USCIA TXBUF register. TX data in the internal buffer is shifted by one bit after the RX data is received.

Workaround

Reinitialize TXBUF before using SPI and after each transmission.
If transmit data needs to be repeated with the next transmission, then write back previously read value:

UCAxTXBUF = UCAxTXBUF;