SWRU626 December 2025 CC3501E , CC3551E
Many use cases don’t want to transmit leftover data of Target Tx FIFO from previous frame of in the next frame. To achieve this in current design, user has to rely on controlled single byte transfers to avoid putting extra data in FIFO. This limits throughout and introduces clock stretch every cycle. A mechanism in needed to flush stale data from Target Tx FIFO before starting a new transaction.
The CC35xx implements a solution to achieve this which gives the flexibility to choose whether to flush or not without adding new interrupt bits. The Target TXEMPTY interrupt is repurposed for this feature.
A status bit TSR.STALE_TXFIFO that tells the software whether the data present inside Target TX FIFO is stale or not.
A control bit TCTR.TXWAIT_STALE_FIFO to enable modified empty indication to Target logic - indicate empty to Target FSM when Tx FIFO is empty OR stale data present in Tx FIFO.
A control bit TCTR.TXEMPTY_ON_TREQ that allows RIS.STXEMPTY interrupt to be used for indicating TREQ condition i.e. the condition when SCL is being stretched waiting for transmit data from the Target.