NXP Semiconductors K22F series, Reference Manual, Page: 1282 / 1407

47.4.4.2 Nine-bit configuration
When C1[M] is set and C4[M10] is cleared, the UART is configured for 9-bit data
characters. If C1[PE] is enabled, the ninth bit is either C3[T8/R8] or the internally
generated parity bit. This results in a frame consisting of a total of 11 bits. In the event
that the ninth data bit is selected to be C3[T8], it will remain unchanged after
transmission and can be used repeatedly without rewriting it, unless the value needs to be
changed. This feature may be useful when the ninth data bit is being used as an address
mark.
When C1[M] and C4[M10] are set, the UART is configured for 9-bit data characters, but
the frame consists of a total of 12 bits. The 12 bits include the start and stop bits, the 9
data character bits, and a tenth internal data bit. Note that if C4[M10] is set, C1[PE] must
also be set. In this case, the tenth bit is the internally generated parity bit. The ninth bit
can either be used as an address mark or a ninth data bit.
See the following table.
Table 47-11. Configuration of 9-bit data formats
C1[PE] UC1[M] C1[M10]
Start
bit
Data
bits
Address
bits
Parity
bits
Stop
bit
0 0 0 See Eight-bit configuration
0 0 1 Invalid configuration
0 1 0 1 9 0 0 1
0 1 0 1 8 1
1
0 1
0 1 1 Invalid Configuration
1 0 0 See Eight-bit configuration
1 0 1 Invalid Configuration
1 1 0 1 8 0 1 1
1 1 1 1 9 0 1 1
1 1 1 1 8 1
1
1 1
1. The address bit identifies the frame as an address character.
Note
Unless in 9-bit mode with M10 set, do not use address mark
wakeup with parity enabled.
Functional description
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
1282 NXP Semiconductors