SWCU193A April 2023 – August 2024 CC2340R2 , CC2340R5 , CC2340R5-Q1
The connections required to use the SPI port are the following four pins:
The device communicating with the bootloader drives the SPI_PICO, SPI_SCLK, and SPI_CS, while the CC23xx drives the SPI_POCI pin.
The format used for SPI communications is the Motorola format with SPH set to 1 and SPO set to 1 (see Figure 20-5 for more information on this format). Refer to the device-specific data sheet for the maximum rate supported on the SPI clock in the peripheral mode.
The controller must take special consideration (regarding the use of the SPI interface) due to the functionality of not configuring any output pins before the external controller device has selected a serial interface.
On the first packet transferred by the controller, no data is received from the bootloader while the bootloader clocks out the bits in the first byte of the packet.
When the bootloader detects that 1 byte has been received on SPI_PICO, the bootloader configures the SPI_POCI output pin.
Before transmitting the next byte in the first packet, the controller must include a small delay to ensure that the bootloader has completed the configuration of the SPI_POCI output pin.