Information
48.3.14 UART Modem Register (UARTx_MODEM)
The MODEM register controls options for setting the modem configuration.
NOTE
RXRTSE, TXRTSPOL, TXRTSE, and TXCTSE must all be
cleared when C7816[ISO7816EN] is enabled. This will cause
the RTS to deassert during ISO-7816 wait times. The ISO-7816
protocol does not use the RTS and CTS signals.
Address: Base address + Dh offset
Bit 7 6 5 4 3 2 1 0
Read 0
RXRTSE TXRTSPOL TXRTSE TXCTSE
Write
Reset
0 0 0 0 0 0 0 0
UARTx_MODEM field descriptions
Field Description
7–4
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
3
RXRTSE
Receiver request-to-send enable
Allows the RTS output to control the CTS input of the transmitting device to prevent receiver overrun.
NOTE: Do not set both RXRTSE and TXRTSE.
0 The receiver has no effect on RTS.
1 RTS is deasserted if the number of characters in the receiver data register (FIFO) is equal to or
greater than RWFIFO[RXWATER]. RTS is asserted when the number of characters in the receiver
data register (FIFO) is less than RWFIFO[RXWATER].
2
TXRTSPOL
Transmitter request-to-send polarity
Controls the polarity of the transmitter RTS. TXRTSPOL does not affect the polarity of the receiver RTS.
RTS will remain negated in the active low state unless TXRTSE is set.
0 Transmitter RTS is active low.
1 Transmitter RTS is active high.
1
TXRTSE
Transmitter request-to-send enable
Controls RTS before and after a transmission.
0 The transmitter has no effect on RTS.
1 When a character is placed into an empty transmitter data buffer , RTS asserts one bit time before the
start bit is transmitted. RTS deasserts one bit time after all characters in the transmitter data buffer
and shift register are completely sent, including the last stop bit. (FIFO)(FIFO)
0
TXCTSE
Transmitter clear-to-send enable
TXCTSE controls the operation of the transmitter. TXCTSE can be set independently from the state of
TXRTSE and RXRTSE.
Table continues on the next page...
Memory map and registers
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
1296
Preliminary
Freescale Semiconductor, Inc.
General Business Information