SPRUJF2A March 2026 – March 2026 AM13E23019
UNICOMM-SPI can be configured to be controller mode by setting the CTL1.CP bit to 1, or in peripheral mode by clearing the CTL1.CP bit. The chip select signal needs to be provided by the controller in four-wire mode and the chip select polarity can be inverted by configuring the PINCM.CSx.INV register. In UNICOMM-SPI peripheral mode, the clock is provided by the controller and used by the peripheral to capture the data. The peripheral has the option to operate in 3-wire or 4-wire mode by configuring the CTL0.FRF field. 4-wire mode only accepts data transfers if the CS is activated.
The CTL0.CSCLR register field determines the behavior of the internal bit counter of the UNICOMM-SPI in peripheral mode when the controller de-asserts the CS signal. This bit is only relevant when the UNICOMM-SPI is configured as a SPI peripheral (CTL1.CP = 0).
When using the Motorola 4-wire mode as a UNICOMM-SPI peripheral with the CTL0.CSCLR = 1 setting, the SPI controller device must follow the below constraints for proper communication. Following these constraints helps the UNICOMM-SPI peripheral to synchronize to the controller during initialization or in the case of a disturbance or glitch on the clock line.