SWCU185G January 2018 – June 2024 CC1312PSIP , CC1312R , CC1352P , CC1352R , CC2642R , CC2642R-Q1 , CC2652P , CC2652PSIP , CC2652R , CC2652RB , CC2652RSIP , CC2662R-Q1
Figure 14-23 and Figure 23-5 show single and continuous transmission signal sequences, respectively, for Motorola SPI format with SPO = 1 and SPH = 0.
In this configuration, the following occurs during idle periods:
If the SSI is enabled and valid data is in the TX FIFO, the SSIFss master signal goes low at the start of transmission and transfers slave data onto the SSIn_RX line of the master immediately. The master SSIn_TX output DIO is enabled.
One-half SSIn_CLK period later, valid master data is transferred to the SSIn_TX line. When both the master and slave data have been set, the SSIn_CLK master clock pin becomes low after one additional half SSIn_CLK period. Data is captured on the falling edges and propagated on the rising edges of the SSIn_CLK signal.
For a single-word transmission after all bits of the data word are transferred, the SSIn_FSS line is returned to its IDLE high state one SSIn_CLK period after the last bit is captured.
For continuous back-to-back transmissions, the SSIn_FSS signal must pulse high between each data word transfer as the slave-select pin freezes the data in its serial peripheral register and keeps it from being altered if the SPH bit is clear. The master device must raise the SSIn_FSS pin of the slave device between each data transfer to enable the serial peripheral data write. When the continuous transfer completes, the SSIn_FSS pin returns to its IDLE state one SSIn_CLK period after the last bit is captured.