SWRU626 December 2025 CC3501E , CC3551E
The RX FIFO in the SDIO peripheral serves as a temporary buffer for incoming data received from the SDIO host via the SDIO data bus protocol. It has a total capacity of 256 bytes and is designed to efficiently handle data flow between the SDIO interface and system memory. The FIFO features a configurable threshold SDIO_CARD_FN1:RXTHR[7:2]VAL, allowing software to define the number of bytes that should accumulate before triggering an interrupt to notify the M33. This mechanism helps optimize data processing by reducing the frequency of interrupts while ensuring timely data handling. To facilitate high-speed data transfer, the FIFO supports DMA, enabling efficient movement of data to system memory without excessive M33 intervention. The DMA block size, which determines how much data is transferred in each operation, must be configured in both the DMA controller and the corresponding SDIO register SDIO_CARD_FN1:DMABLKTHR[2:0]RXDMABLK to ensure proper synchronization between the FIFO and memory. Additionally, a dedicated register SDIO_CARD_FN1:FLUSHCMD[0]RXBUF allows software to flush the FIFO when necessary, ensuring that unwanted or stale data does not interfere with new transmissions. A status register SDIO_CARD_FN1:RXBBUF[10:0]VAL provides real-time visibility into the number of bytes currently stored in the FIFO, allowing software to monitor and manage data flow effectively. These features together ensure robust and efficient handling of received SDIO data, minimizing latency and maximizing system performance.