NXP Semiconductors K22F series, Reference Manual, Page: 1247 / 1407

UARTx_RWFIFO field descriptions
Field Description
RXWATER Receive Watermark
When the number of datawords in the receive FIFO/buffer is equal to or greater than the value in this
register field, an interrupt via S1[RDRF] or a DMA request via C5[RDMAS] is generated as determined by
C5[RDMAS] and C2[RIE]. For proper operation, the value in RXWATER must be set to be less than the
receive FIFO/buffer size as indicated by PFIFO[RXFIFOSIZE] and PFIFO[RXFE] and must be greater
than 0.
47.3.22 UART FIFO Receive Count (UARTx_RCFIFO)
This is a read only register that indicates how many datawords are currently in the receive
FIFO/buffer. It may be read at any time.
Address: Base a 16h offset
Bit 7 6 5 4 3 2 1 0
Read RXCOUNT
Write
Reset 0 0 0 0 0 0 0 0
UARTx_RCFIFO field descriptions
Field Description
RXCOUNT Receive Counter
The value in this register indicates the number of datawords that are in the receive FIFO/buffer. If a
dataword is being received, that is, in the receive shift register, it is not included in the count. This value
may be used in conjunction with PFIFO[RXFIFOSIZE] to calculate how much room is left in the receive
FIFO/buffer.
47.3.23 UART 7816 Control Register (UARTx_C7816)
The C7816 register is the primary control register for ISO-7816 specific functionality.
This register is specific to 7816 functionality and the values in this register have no effect
on UART operation and should be ignored if ISO_7816E is not set/enabled. This register
may be read at any time but values must be changed only when ISO_7816E is not set.
Address: Base a 18h offset
Bit 7 6 5 4 3 2 1 0
Read 0
ONACK ANACK INIT TTYPE ISO_7816E
Write
Reset 0 0 0 0 0 0 0 0
Chapter 47 Universal Asynchronous Receiver/Transmitter (UART)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 1247