SWCU195A December 2024 – May 2025 CC2744R7-Q1 , CC2745P10-Q1 , CC2745R10-Q1 , CC2745R7-Q1 , CC2755R10
The common TX FIFO is a 16-bit wide, eight location deep, first-in first-out memory buffer given the selected SPI data frame size is greater than 8 bits. The organization of this FIFO is modified dynamically if the selected SPI data frame size is greater than 8 bits, the common TX FIFO is a 16-bit wide, 8 location deep, first-in first-out memory buffer. The CPU writes data to the FIFO via the SPI.TXDATA register and data are stored in the FIFO until the data is read out by the transmission logic.
When configured as a controller (or a peripheral), parallel data is written into the TX FIFO before serial conversion and transmission to the attached peripheral (or controller) through the PICO (or POCI) pin.
In peripheral mode, the SPI transmits data each time the controller initiates a transaction. If the TX FIFO is empty and the controller initiates a transaction, the peripheral will transmit garbage data. The user or software is responsible for making valid data available in the FIFO as needed. The SPI can be configured to generate an interrupt when a configurable level within the FIFO is selected via SPI:IFLS, or a μDMA request when the FIFO is not FULL.