SWRU543B January 2019 – June 2025 CC3230S , CC3230SF , CC3235MODS , CC3235MODSF , CC3235S , CC3235SF
This section describes SPI full-duplex transmission with the SPI mode1 and SPI mode3. In the transfer format with PHA = 1, SPIEN is activated a delay (tLead) ahead of the first SPICLK edge. In both master and slave modes, the SPI drives the data lines on the first SPICLK edge.
Each data frame is transmitted starting with the MSB. At the extremity of both SPI data lines, the first bit of the SPI word is valid on the next SPICLK edge, a half-cycle of SPICLK later, and is the sampling edge for both the master and slave. When the third edge occurs, the received data bit is shifted into the shift register. The next data bit of the master is provided to the serial input pin of the slave. This process continues for a total number of pulses on the SPICLK line defined by the word length programmed in the master device, with data being latched on even-numbered edges and shifted on odd-numbered edges.
Figure 8-5 is a timing diagram of a SPI transfer for the SPI mode1 and SPI mode3, when the SPI is master or slave, with the frequency of SPICLK equal to the frequency of CLKSPIREF.
Figure 8-5 Full-Duplex Single Transfer Format With PHA = 1In 3-pin mode without using the SPIEN signal, the controller provides the same waveform, with SPIEN forced to low state. In 3-pin slave mode, SPIEN is useless.