UARTx_TWFIFO field descriptionsField DescriptionTXWATER Transmit WatermarkWhen the number of datawords in the transmit FIFO/buffer is equal to or less than the value in this registerfield, an interrupt via S1[TDRE] or a DMA request via C5[TDMAS] is generated as determined byC5[TDMAS] and C2[TIE]. For proper operation, the value in TXWATER must be set to be less than thesize of the transmit buffer/FIFO size as indicated by PFIFO[TXFIFOSIZE] and PFIFO[TXFE].47.3.20 UART FIFO Transmit Count (UARTx_TCFIFO)This is a read only register that indicates how many datawords are currently in thetransmit buffer/FIFO. It may be read at any time.Address: Base address + 14h offsetBit 7 6 5 4 3 2 1 0Read TXCOUNTWriteReset 0 0 0 0 0 0 0 0UARTx_TCFIFO field descriptionsField DescriptionTXCOUNT Transmit CounterThe value in this register indicates the number of datawords that are in the transmit FIFO/buffer. If adataword is being transmitted, that is, in the transmit shift register, it is not included in the count. Thisvalue may be used in conjunction with PFIFO[TXFIFOSIZE] to calculate how much room is left in thetransmit FIFO/buffer.47.3.21 UART FIFO Receive Watermark (UARTx_RWFIFO)This register provides the ability to set a programmable threshold for notification of theneed to remove data from the receiver FIFO/buffer. This register may be read at any timebut must be written only when C2[RE] is not asserted. Changing the value in this registerwill not clear S1[RDRF].Address: Base address + 15h offsetBit 7 6 5 4 3 2 1 0Read RXWATERWriteReset 0 0 0 0 0 0 0 1Memory map and registersK22F Sub-Family Reference Manual, Rev. 4, 08/20161246 NXP Semiconductors
