Microchip Technology DV164136 Data Sheet
2007-2012 Microchip Technology Inc.
DS39778E-page 53
PIC18F87J11 FAMILY
4.4.3
RC_IDLE MODE
In RC_IDLE mode, the CPU is disabled but the
peripherals continue to be clocked from the internal
oscillator block. This mode allows for controllable
power conservation during Idle periods.
From RC_RUN, this mode is entered by setting the
IDLEN bit and executing a SLEEP instruction. If the
device is in another Run mode, first set IDLEN, then
clear the SCSx bits and execute SLEEP. When the
clock source is switched to the INTOSC block, the pri-
mary oscillator is shut down and the OSTS bit is
cleared.
When a wake event occurs, the peripherals continue to
be clocked from the internal oscillator block. After a
delay of T
peripherals continue to be clocked from the internal
oscillator block. This mode allows for controllable
power conservation during Idle periods.
From RC_RUN, this mode is entered by setting the
IDLEN bit and executing a SLEEP instruction. If the
device is in another Run mode, first set IDLEN, then
clear the SCSx bits and execute SLEEP. When the
clock source is switched to the INTOSC block, the pri-
mary oscillator is shut down and the OSTS bit is
cleared.
When a wake event occurs, the peripherals continue to
be clocked from the internal oscillator block. After a
delay of T
CSD
following the wake event, the CPU
begins executing code being clocked by the INTRC.
The IDLEN and SCSx bits are not affected by the
wake-up. The INTRC source will continue to run if
either the WDT or the Fail-Safe Clock Monitor is
enabled.
The IDLEN and SCSx bits are not affected by the
wake-up. The INTRC source will continue to run if
either the WDT or the Fail-Safe Clock Monitor is
enabled.
4.5
Exiting Idle and Sleep Modes
An exit from Sleep mode, or any of the Idle modes, is
triggered by an interrupt, a Reset or a WDT 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 sections (see
triggered by an interrupt, a Reset or a WDT 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 sections (see
).
4.5.1
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.
On all exits from Idle or Sleep modes by interrupt, code
execution branches to the interrupt vector if the
GIE/GIEH bit (INTCON<7>) is set. Otherwise, code
execution continues or resumes without branching
(see
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.
On all exits from Idle or Sleep modes by interrupt, code
execution branches to the interrupt vector if the
GIE/GIEH bit (INTCON<7>) is set. Otherwise, code
execution continues or resumes 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.
delay is required for the CPU to prepare for execution.
Instruction execution resumes on the first clock cycle
following this delay.
4.5.2
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
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
result in a WDT Reset (see
The Watchdog Timer and postscaler are cleared by one
of the following events:
• Executing a SLEEP or CLRWDT instruction
• The loss of a currently selected clock source (if
of the following events:
• Executing a SLEEP or CLRWDT instruction
• The loss of a currently selected clock source (if
the Fail-Safe Clock Monitor is enabled)
4.5.3
EXIT BY RESET
Exiting an Idle or Sleep mode by Reset automatically
forces the device to run from the INTRC.
forces the device to run from the INTRC.
4.5.4
EXIT WITHOUT AN OSCILLATOR
START-UP DELAY
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
invoke the OST at all. There are two cases:
• PRI_IDLE mode, where the primary clock source
is not stopped
• The primary clock source is either the EC or
ECPLL mode
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 (EC). However, a
fixed delay of interval, T
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 (EC). 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.
allow the CPU to prepare for execution. Instruction
execution resumes on the first clock cycle following this
delay.