UARTx_S2 field descriptions (continued)
Field
Description
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.
46.3.7 UART Control Register 3 (UARTx_C3)
Writing R8 does not have any effect. TXDIR and TXINV can be changed only between
transmit and receive packets.
Address: Base a 6h offset
Bit
7
6
5
4
3
2
1
0
Read
Write
Reset
0
0
0
0
0
0
0
0
UARTx_C3 field descriptions
Field
Description
7
R8
Received Bit 8
R8 is the ninth data bit received when the UART is configured for 9-bit data format, that is, if C1[M] = 1 or
C4[M10] = 1. The R8 value corresponds to the current data value in the UARTx_D register. To read the
9th bit, read the value of UARTx_C3[R8], then read the UARTx_D register.
6
T8
Transmit Bit 8
T8 is the ninth data bit transmitted when the UART is configured for 9-bit data format, that is, if C1[M] = 1
or C4[M10] = 1.
NOTE: If the value of T8 is the same as in the previous transmission, T8 does not have to be rewritten.
The same value is transmitted until T8 is rewritten.
To correctly transmit the 9th bit, write UARTx_C3[T8] to the desired value, then write the
UARTx_D register with the remaining data.
5
TXDIR
Transmitter Pin Data Direction in Single-Wire mode
Determines whether the TXD pin is used as an input or output in the single-wire mode of operation. This
field is relevant only to the single wire mode. When C7816[ISO7816E] is set/enabled and C7816[TTYPE]
= 1, this field is automatically cleared after the requested block is transmitted. This condition is detected
when TL7816[TLEN] = 0 and 4 additional characters are transmitted. Additionally, if C7816[ISO7816E] is
set/enabled and C7816[TTYPE] = 0 and a NACK is being transmitted, the hardware automatically
overrides this field as needed. In this situation, TXDIR does not reflect the temporary state associated with
the NACK.
Table continues on the next page...
Memory map and registers
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
1148
Freescale Semiconductor, Inc.