NXP Semiconductors KL25 Series - Functional Description

UARTx_C4 field descriptions
Field Description
7
TDMAS
Transmitter DMA Select
TDMAS configures the transmit data register empty flag, TDRE, to generate interrupt or DMA requests if
TIE is set.
NOTE: If UART_C2[TIE] is cleared, TDRE DMA and TDRE interrupt request signals are not asserted
when the TDRE flag is set, regardless of the state of TDMAS.
If UART_C2[TIE] and TDMAS are both set, then UART_C2[TCIE] must be cleared, and UART_D
must not be written outside of servicing of a DMA request.
0 If TIE is set and the TDRE flag is set, the TDRE interrupt request signal is asserted to request
interrupt service.
1 If TIE is set and the TDRE flag is set, the TDRE DMA request signal is asserted to request a DMA
transfer.
6
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
5
RDMAS
Receiver Full DMA Select
RDMAS configures the receiver data register full flag, RDRF, to generate interrupt or DMA requests if RIE
is set.
NOTE: If RIE is cleared, the RDRF DMA and RDRF interrupt request signals are not asserted when the
RDRF flag is set, regardless of the state of RDMAS.
0 If RIE is set and the RDRF flag is set, the RDRF interrupt request signal is asserted to request
interrupt service.
1 If RIE is set and the RDRF flag is set, the RDRF DMA request signal is asserted to request a DMA
transfer.
4
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
3
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
2–0
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
40.3 Functional description
The UART allows full-duplex, asynchronous, NRZ serial communication among the
MCU and remote devices, including other MCUs. The UART comprises a baud rate
generator, transmitter, and receiver block. The transmitter and receiver operate
independently, although they use the same baud rate generator. During normal operation,
the MCU monitors the status of the UART, writes the data to be transmitted, and
processes received data. The following describes each of the blocks of the UART.
Chapter 40 Universal Asynchronous Receiver/Transmitter (UART1 and UART2)
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
Freescale Semiconductor, Inc. 761