Microchip Technology MA160014 Data Sheet

DS41412F-page 54

 2010-2012 Microchip Technology Inc.

An exit from Sleep mode or any of the Idle modes is
triggered by any one of the following:

• an interrupt

• a  Reset

• a Watchdog Time-out

This section discusses the triggers that cause exits
from power-managed modes. The clocking subsystem
actions are discussed in each of the power-managed
modes (see 

 and 

). 

3.5.1

EXIT BY INTERRUPT

Any of the available interrupt sources can cause the
device to exit from an Idle mode or the Sleep mode to
a Run mode. To enable this functionality, an interrupt
source must be enabled by setting its enable bit in one
of the INTCON or PIE registers. The exit sequence is
initiated when the corresponding interrupt flag bit is set.

The instruction immediately following the SLEEP
instruction is executed on all exits by interrupt from Idle
or Sleep modes. Code execution then branches to the
interrupt vector if the GIE/GIEH bit of the INTCON
register is set, otherwise code execution continues
without branching (see 

A fixed delay of interval T

CSD

 following the wake event

is required when leaving Sleep and Idle modes. This
delay is required for the CPU to prepare for execution.
Instruction execution resumes on the first clock cycle
following this delay.

3.5.2

EXIT BY WDT TIME-OUT

A WDT time-out will cause different actions depending
on which power-managed mode the device is in when
the time-out occurs.

If the device is not executing code (all Idle modes and
Sleep mode), the time-out will result in an exit from the
power-managed mode (see 

 and 

). If the device

is executing code (all Run modes), the time-out will
result in a WDT Reset (see 

The WDT timer and postscaler are cleared by any one
of the following:

• executing a SLEEP instruction

• executing a CLRWDT instruction

• the loss of the currently selected clock source 

when the Fail-Safe Clock Monitor is enabled 

• modifying the IRCF bits in the OSCCON register 

when the internal oscillator block is the device 
clock source

3.5.3

EXIT BY RESET

Exiting Sleep and Idle modes by Reset causes code
execution to restart at address 0. See 

 for more details. 

The exit delay time from Reset to the start of code
execution depends on both the clock sources before
and after the wake-up and the type of oscillator.

3.5.4

EXIT WITHOUT AN OSCILLATOR 
START-UP DELAY

Certain exits from power-managed modes do not
invoke the OST at all. There are two cases:

• PRI_IDLE mode, where the primary clock source 

is not stopped and

• the primary clock source is not any of the LP, XT, 

HS or HSPLL modes.

In these instances, the primary clock source either
does not require an oscillator start-up delay since it is
already running (PRI_IDLE), or normally does not
require an oscillator start-up delay (RC, EC, INTOSC,
and INTOSCIO modes). However, a fixed delay of
interval T

CSD

 following the wake event is still required

when leaving Sleep and Idle modes to allow the CPU
to prepare for execution. Instruction execution resumes
on the first clock cycle following this delay.