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UARTx_S2 field descriptions (continued)
Field
Description
Setting this field reverses the polarity of the received data input. In NRZ format, a one is represented by a
mark and a zero is represented by a space for normal polarity, and the opposite for inverted polarity. This
field is automatically set when C7816[INIT] and C7816[ISO7816E] are enabled and an initial character is
detected in T = 0 protocol mode.
NOTE: Setting RXINV inverts the RxD input for data bits, start and stop bits, break, and idle. When
C7816[ISO7816E] is set/enabled, only the data bits and the parity bit are inverted.
0
Receive data is not inverted.
1
Receive data is inverted.
3
RWUID
Receive Wakeup Idle Detect
When RWU is set and WAKE is cleared, this field controls whether the idle character that wakes the
receiver sets S1[IDLE]. This field must be cleared when C7816[ISO7816E] is set/enabled.
0
S1[IDLE] is not set upon detection of an idle character.
1
S1[IDLE] is set upon detection of an idle character.
2
BRK13
Break Transmit Character Length
Determines whether the transmit break character is 10, 11, or 12 bits long, or 13 or 14 bits long. See for
the length of the break character for the different configurations. The detection of a framing error is not
affected by this field.
0
Break character is 10, 11, or 12 bits long.
1
Break character is 13 or 14 bits long.
1
Reserved
Reserved.
This field is reserved.
0
RAF
Receiver Active Flag
RAF is set when the UART receiver detects a logic 0 during the RT1 time period of the start bit search.
RAF is cleared when the receiver detects an idle character when C7816[ISO7816E] is cleared/disabled.
When C7816[ISO7816E] is enabled, the RAF is cleared if the C7816[TTYPE] = 0 expires or the
C7816[TTYPE] = 1 expires.
NOTE: In case C7816[ISO7816E] is set and C7816[TTYPE] = 0, it is possible to configure the guard time
to 12. However, if a NACK is required to be transmitted, the data transfer actually takes 13 ETU
with the 13th ETU slot being a inactive buffer. Therefore, in this situation, the RAF may deassert
one ETU prior to actually being inactive.
0
UART receiver idle/inactive waiting for a start bit.
1
UART receiver active, RxD input not idle.
Memory map and registers
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
690
Freescale Semiconductor, Inc.