Microchip Technology MA300015 Data Sheet

DS70150E-page 124

© 2011 Microchip Technology Inc.

To allow the system to determine baud rates of
received characters, the input can be optionally linked
to a selected capture input. To enable this mode, the
user must program the input capture module to detect
the falling and rising edges of the Start bit.

18.10.1

UART OPERATION DURING CPU 
SLEEP MODE

When the device enters Sleep mode, all clock sources
to the module are shut down and stay at logic ‘0’. If
entry into Sleep mode occurs while a transmission is
in progress, then the transmission is aborted. The
UxTX pin is driven to logic ‘1’. Similarly, if entry into
Sleep mode occurs while a reception is in progress,
then the reception is aborted. The UxSTA, UxMODE,
Transmit and Receive registers and buffers, and the
UxBRG register are not affected by Sleep mode.

If the Wake bit (UxMODE<7>) is set before the device
enters Sleep mode, then a falling edge on the UxRX
pin will generate a receive interrupt. The Receive
Interrupt Select Mode bit (URXISEL) has no effect for
this function. If the receive interrupt is enabled, then
this will wake-up the device from Sleep. The UARTEN
bit must be set in order to generate a wake-up
interrupt.

18.10.2

UART OPERATION DURING CPU 
IDLE MODE

For the UART, the USIDL bit selects if the module will
stop operation when the device enters Idle mode, or
whether the module will continue on Idle. If USIDL = 0,
the module will continue operation during Idle mode. If
USIDL = 1, the module will stop on Idle.