SWCU194 March 2023 CC1314R10 , CC1354P10 , CC1354R10 , CC2674P10 , CC2674R10
The connections required to use the SPI port are the following four pins:
SPI0_CLK
SPI0_CS
SPI0_MOSI
SPI0_MISO
The device communicating with the bootloader drives the SPI0_CLK, SPI0_MOSI and SPI0_CS pins, while the CC13x4x10 and CC26x4x10 device platform drives the SPI0_MISO pin.
The format used for SPI communications is the Motorola format with SPH set to 1 and SPO set to 1 (see Figure 23-9 for more information on this format). The SPI interface has a hardware requirement that limits the maximum rate of SPI0_CLK to be at most 1/12 of the frequency of the SPI module clock
The host device must take special consideration (regarding the use of the SPI interface) due to the bootloader not configuring any output pins before the host device has selected a serial interface.
On the first packet transferred by the host device, no data is received from the bootloader while the bootloader clocks out the bits in the first byte of the packet.
Once the bootloader detects that 1 byte has been received on the SPI interface, the bootloader finally configures the SPI0_MISO output pin.
Before transmitting the next byte in the first packet, the host device must include a small delay to ensure that the bootloader has completed the configuration of the SPI0_MISO output pin.