If the associated error was detected in the received character that caused
UART_S1[RDRF] to be set, the error flags - noise flag (UART_S1[NF]), framing error
(UART_S1[FE]), and parity error flag (UART_S1[PF]) - are set at the same time as
UART_S1[RDRF]. These flags are not set in overrun cases.
If UART_S1[RDRF] was already set when a new character is ready to be transferred
from the receive shifter to the receive data buffer, the overrun (UART_S1[OR]) flag is
set instead of the data along with any associated NF, FE, or PF condition is lost.
At any time, an active edge on the UART_RX serial data input pin causes the
UART_S2[RXEDGIF] flag to set. The UART_S2[RXEDGIF] flag is cleared by writing a
1 to it. This function depends on the receiver being enabled (UART_C2[RE] = 1).
Functional description
KL02 Sub-Family Reference Manual, Rev. 2.1, July 2013
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Freescale Semiconductor, Inc.