Microchip Technology MA160014 Data Sheet
2010-2012 Microchip Technology Inc.
DS41412F-page 47
PIC18(L)F2X/4XK22
3.0
POWER-MANAGED MODES
PIC18(L)F2X/4XK22 devices offer a total of seven
operating modes for more efficient power manage-
ment. These modes provide a variety of options for
selective power conservation in applications where
resources may be limited (i.e., battery-powered
devices).
operating modes for more efficient power manage-
ment. These modes provide a variety of options for
selective power conservation in applications where
resources may be limited (i.e., battery-powered
devices).
There are three categories of power-managed modes:
• Run modes
• Idle modes
• Sleep mode
These categories define which portions of the device
are clocked and sometimes, what speed. The Run and
Idle modes may use any of the three available clock
sources (primary, secondary or internal oscillator
block). The Sleep mode does not use a clock source.
are clocked and sometimes, what speed. The Run and
Idle modes may use any of the three available clock
sources (primary, secondary or internal oscillator
block). The Sleep mode does not use a clock source.
The power-managed modes include several power-
saving features offered on previous PIC
saving features offered on previous PIC
®
microcontroller
devices.
One of the clock switching features allows the
controller to use the secondary oscillator (SOSC) in
place of the primary oscillator. Also included is the Sleep
mode, offered by all PIC
place of the primary oscillator. Also included is the Sleep
mode, offered by all PIC
®
microcontroller devices, where
all device clocks are stopped.
3.1
Selecting Power-Managed Modes
Selecting a power-managed mode requires two
decisions:
decisions:
• Whether or not the CPU is to be clocked
• The selection of a clock source
The IDLEN bit (OSCCON<7>) controls CPU clocking,
while the SCS<1:0> bits (OSCCON<1:0>) select the
clock source. The individual modes, bit settings, clock
sources and affected modules are summarized in
while the SCS<1:0> bits (OSCCON<1:0>) select the
clock source. The individual modes, bit settings, clock
sources and affected modules are summarized in
3.1.1
CLOCK SOURCES
The SCS<1:0> bits allow the selection of one of three
clock sources for power-managed modes. They are:
clock sources for power-managed modes. They are:
• the primary clock, as defined by the FOSC<3:0>
Configuration bits
• the secondary clock (the SOSC oscillator)
• the internal oscillator block
3.1.2
ENTERING POWER-MANAGED
MODES
MODES
Switching from one power-managed mode to another
begins by loading the OSCCON register. The
SCS<1:0> bits select the clock source and determine
which Run or Idle mode is to be used. Changing these
bits causes an immediate switch to the new clock
source, assuming that it is running. The switch may
also be subject to clock transition delays. Refer to
begins by loading the OSCCON register. The
SCS<1:0> bits select the clock source and determine
which Run or Idle mode is to be used. Changing these
bits causes an immediate switch to the new clock
source, assuming that it is running. The switch may
also be subject to clock transition delays. Refer to
for more information.
Entry to the power-managed Idle or Sleep modes is
triggered by the execution of a SLEEP instruction. The
actual mode that results depends on the status of the
IDLEN bit.
triggered by the execution of a SLEEP instruction. The
actual mode that results depends on the status of the
IDLEN bit.
Depending on the current mode and the mode being
switched to, a change to a power-managed mode does
not always require setting all of these bits. Many
transitions may be done by changing the oscillator select
bits, or changing the IDLEN bit, prior to issuing a SLEEP
instruction. If the IDLEN bit is already configured
correctly, it may only be necessary to perform a SLEEP
instruction to switch to the desired mode.
switched to, a change to a power-managed mode does
not always require setting all of these bits. Many
transitions may be done by changing the oscillator select
bits, or changing the IDLEN bit, prior to issuing a SLEEP
instruction. If the IDLEN bit is already configured
correctly, it may only be necessary to perform a SLEEP
instruction to switch to the desired mode.
TABLE 3-1:
POWER-MANAGED MODES
Mode
OSCCON Bits
Module Clocking
Available Clock and Oscillator Source
IDLEN
(1)
SCS<1:0>
CPU
Peripherals
Sleep
0
N/A
Off
Off
None – All clocks are disabled
PRI_RUN
N/A
00
Clocked
Clocked
Primary – LP, XT, HS, RC, EC and Internal
Oscillator Block
Oscillator Block
(2)
.
This is the normal full-power execution mode.
SEC_RUN
N/A
01
Clocked
Clocked
Secondary – SOSC Oscillator
RC_RUN
N/A
1x
Clocked
Clocked
Internal Oscillator Block
(2)
PRI_IDLE
1
00
Off
Clocked
Primary – LP, XT, HS, HSPLL, RC, EC
SEC_IDLE
1
01
Off
Clocked
Secondary – SOSC Oscillator
RC_IDLE
1
1x
Off
Clocked
Internal Oscillator Block
(2)
Note 1:
IDLEN reflects its value when the SLEEP instruction is executed.
2:
Includes HFINTOSC and HFINTOSC postscaler, as well as the LFINTOSC source.