The RxFIFO stores data that is received by the receiver serial shift register. The RxFIFO’s maximum data width is eight bits.
When data is loaded into the RxFIFO, the RxFIFO empty flag is cleared and this state remains Low until all data in the RxFIFO has been transferred through the APB interface. Reading from an empty RxFIFO returns zero.
The RxFIFO full status (Chnl_int_sts [RXFULL] and Channel_sts [RXFULL] bits) indicates that the RxFIFO is full and prevents any further data from being loaded into the RxFIFO. When a space becomes available in the RxFIFO, any character stored in the receiver will be loaded.
A threshold trigger (RTRIG) can be setup on the RxFIFO fill level. The Receiver Trigger Level register (Rcvr_FIFO_trigger_level) can be used to setup this value, such that the trigger is set when the RxFIFO fill level transitions this programmed value. The Range is 1 to 63.