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flag is often used in systems with modems to determine when it is safe to turn off the
modem. If the transmit complete interrupt enable (LPUART_CTRL[TCIE]) bit is set, a
hardware interrupt is requested when LPUART_STAT[TC] is set. Instead of hardware
interrupts, software polling may be used to monitor the LPUART_STAT[TDRE] and
LPUART_STAT[TC] status flags if the corresponding LPUART_CTRL[TIE] or
LPUART_CTRL[TCIE] local interrupt masks are cleared.
When a program detects that the receive data register is full (LPUART_STAT[RDRF] =
1), it gets the data from the receive data register by reading LPUART_DATA. The
LPUART_STAT[RDRF] flag is cleared by reading LPUART_DATA.
The IDLE status flag includes logic that prevents it from getting set repeatedly when the
LPUART_RX line remains idle for an extended period of time. IDLE is cleared by
writing 1 to the LPUART_STAT[IDLE] flag. After LPUART_STAT[IDLE] has been
cleared, it cannot become set again until the receiver has received at least one new
character and has set LPUART_STAT[RDRF].
If the associated error was detected in the received character that caused
LPUART_STAT[RDRF] to be set, the error flags - noise flag (LPUART_STAT[NF]),
framing error (LPUART_STAT[FE]), and parity error flag (LPUART_STAT[PF]) - are
set at the same time as LPUART_STAT[RDRF]. These flags are not set in overrun cases.
If LPUART_STAT[RDRF] was already set when a new character is ready to be
transferred from the receive shifter to the receive data buffer, the overrun
(LPUART_STAT[OR]) flag is set instead of the data along with any associated NF, FE,
or PF condition is lost.
If the received character matches the contents of MATCH[MA1] and/or MATCH[MA2]
then the LPUART_STAT[MA1F] and/or LPUART_STAT[MA2F] flags are set at the
same time that LPUART_STAT[RDRF] is set.
At any time, an active edge on the LPUART_RX serial data input pin causes the
LPUART_STAT[RXEDGIF] flag to set. The LPUART_STAT[RXEDGIF] flag is
cleared by writing a 1 to it. This function depends on the receiver being enabled
(LPUART_CTRL[RE] = 1).
Functional description
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
676
Freescale Semiconductor, Inc.