Information

45.1.2.2 Wait mode
UART operation in the Wait mode depends on the state of the C1[UARTSWAI] field.
• If C1[UARTSWAI] is cleared, and the CPU is in Wait mode, the UART operates
normally.
• If C1[UARTSWAI] is set, and the CPU is in Wait mode, the UART clock generation
ceases and the UART module enters a power conservation state.
C1[UARTSWAI] does not initiate any power down or power up procedures for the
ISO-7816 smartcard interface.
Setting C1[UARTSWAI] does not affect the state of the C2[RE] or C2[TE].
If C1[UARTSWAI] is set, any ongoing transmission or reception stops at the Wait mode
entry. The transmission or reception resumes when either an internal or external interrupt
brings the CPU out of Wait mode. Bringing the CPU out of Wait mode by reset aborts
any ongoing transmission or reception and resets the UART.
45.1.2.3 Stop mode
The UART is inactive during Stop mode for reduced power consumption. The STOP
instruction does not affect the UART register states, but the UART module clock is
disabled. The UART operation resumes after an external interrupt brings the CPU out of
Stop mode. Bringing the CPU out of Stop mode by reset aborts any ongoing transmission
or reception and resets the UART. Entering or leaving Stop mode does not initiate any
power down or power up procedures for the ISO-7816 smartcard interface.
45.2 UART signal descriptions
The UART signals are shown in the following table.
Table 45-1. UART signal descriptions
Signal Description I/O
CTS Clear to send I
RTS Request to send O
RXD Receive data I
TXD Transmit data O
Collision Collision detect I
UART signal descriptions
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
1044 Freescale Semiconductor, Inc.