Information

UARTx_C2 field descriptions (continued)
Field Description
transmitting. As long as SBK is set, the transmitter continues to send complete break characters (10, 11,
or 12 bits, or 13 or 14 bits).
• 10, 11, or 12 logic 0s if S2[BRK13] is cleared
• 13 or 14 logic 0s if S2[BRK13] is set.
Transmitting break charactersThis field must be cleared when C7816[ISO_7816E] is set.
0 Normal transmitter operation.
1 Queue break characters to be sent.
48.3.5 UART Status Register 1 (UARTx_S1)
The S1 register provides inputs to the MCU for generation of UART interrupts or DMA
requests. This register can also be polled by the MCU to check the status of its fields. To
clear a flag, the status register should be read followed by a read or write to D register,
depending on the interrupt flag type. Other instructions can be executed between the two
steps as long the handling of I/O is not compromised, but the order of operations is
important for flag clearing. When a flag is configured to trigger a DMA request, assertion
of the associated DMA done signal from the DMA controller clears the flag.
NOTE
• If the condition that results in the assertion of the flag,
interrupt, or DMA request is not resolved prior to clearing
the flag, the flag, and interrupt/DMA request, reasserts. For
example, if the DMA or interrupt service routine fails to
write sufficient data to the transmit buffer to raise it above
the watermark level, the flag reasserts and generates
another interrupt or DMA request.
• Reading an empty data register to clear one of the flags of
the S1 register causes the FIFO pointers to become
misaligned. A receive FIFO flush reinitializes the pointers.
Address: Base address + 4h offset
Bit 7 6 5 4 3 2 1 0
Read TDRE TC RDRF IDLE OR NF FE PF
Write
Reset
1 1 0 0 0 0 0 0
Chapter 48 Universal Asynchronous Receiver/Transmitter (UART)
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
Freescale Semiconductor, Inc.
Preliminary
1285
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