NXP Semiconductors K22F series, Reference Manual, Page: 1331 / 1407

48.3.3.2.6 Match On Match Off operation
Match on, match off operation is enabled when both LPUART_BAUD[MAEN1] and
LPUART_BAUD[MAEN2] are set and LPUART_BAUD[MATCFG] is equal to 10. In
this function, a character received by the LPUART_RX pin that matches MATCH[MA1]
is received and transferred to the receive buffer, and LPUART_STAT[RDRF] is set. All
subsequent characters are considered to be data and are also transferred to the receive
data buffer, until a character is received that matches MATCH[MA2] register. The
character that matches MATCH[MA2] and all following characters are discarded, this
continues until another character that matches MATCH[MA1] is received. If both the
LPUART_BAUD[MAEN1] and LPUART_BAUD[MAEN2] bits are negated, the
receiver operates normally and all data received is transferred to the receive data buffer.
NOTE
Match on, match off operation requires both
LPUART_BAUD[MAEN1] and LPUART_BAUD[MAEN2] to
be asserted.
48.3.3.3 Hardware flow control
To support hardware flow control, the receiver can be programmed to automatically
deassert and assert LPUART_RTS.
• LPUART_RTS remains asserted until the transfer is complete, even if the transmitter
is disabled midway through a data transfer. See Transceiver driver enable using
LPUART_RTS for more details.
• If the receiver request-to-send functionality is enabled, the receiver automatically
deasserts LPUART_RTS if the number of characters in the receiver data register is
full or a start bit is detected that will cause the receiver data register to be full.
• The receiver asserts LPUART_RTS when the number of characters in the receiver
data register is not full and has not detected a start bit that will cause the receiver data
register to be full. It is not affected if STAT[RDRF] is asserted.
• Even if LPUART_RTS is deasserted, the receiver continues to receive characters
until the receiver data buffer is overrun.
• If the receiver request-to-send functionality is disabled, the receiver LPUART_RTS
remains deasserted.
Chapter 48 Low Power Universal Asynchronous Receiver/Transmitter (LPUART)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 1331