NXP Semiconductors MKW01Z128, Reference Manual, Page: 769 / 884

shifter, write 1, and then write 0 to the UART_C2[SBK] bit. This action queues a break
character to be sent as soon as the shifter is available. If UART_C2[SBK] remains 1
when the queued break moves into the shifter, synchronized to the baud rate clock, an
additional break character is queued. If the receiving device is another Freescale
Semiconductor UART, the break characters are received as 0s in all data bits and a
framing error (UART_S1[FE] = 1) occurs.
When idle-line wakeup is used, a full character time of idle (logic 1) is needed between
messages to wake up any sleeping receivers. Normally, a program would wait for
UART_S1[TDRE] to become set to indicate the last character of a message has moved to
the transmit shifter, then write 0 and then write 1 to the UART_C2[TE] bit. This action
queues an idle character to be sent as soon as the shifter is available. As long as the
character in the shifter does not finish whileUART_C2[TE] is cleared, the UART
transmitter never actually releases control of the UART_TX pin.
The length of the break character is affected by the UART_S2[BRK13], UART_C1[M]
and UART_C4[M10] bits as shown below.
Table 32-1. Break character length
BRK13 M M10 SBNS Break character
length
0 0 0 0 10 bit times
0 0 0 1 11 bit times
0 1 0 0 11 bit times
0 1 0 1 12 bit times
0 X 1 0 12 bit times
0 X 1 1 13 bit times
1 0 0 0 13 bit times
1 0 0 1 14 bit times
1 1 0 0 14 bit times
1 1 0 1 15 bit times
1 X 1 0 15 bit times
1 X 1 1 16 bit times
32.3.3 Receiver functional description
In this section, the receiver block diagram is a guide for the overall receiver functional
description.
Next, the data sampling technique used to reconstruct receiver data is described in more
detail. Finally, two variations of the receiver wakeup function are explained.
Functional description
MKW01Z128 MCU Reference Manual, Rev. 3, 04/2016
638 Freescale Semiconductor, Inc.