PIC18F-LF1XK50 MICROCHIP [Microchip Technology], PIC18F-LF1XK50 Datasheet - Page 235

• Manufacturer Part Number: PIC18F-LF1XK50
• Description: 20-Pin USB Flash Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

19.0
PIC18F/LF1XK50 devices offer a total of seven operat-
ing modes for more efficient power management.
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.
The power-managed modes include several power-
saving features offered on previous PIC
devices. One is the clock switching feature which allows
the controller to use the Timer1 oscillator in place of the
primary oscillator. Also included is the Sleep mode,
offered by all PIC
device clocks are stopped.
19.1
Selecting a power-managed mode requires two
decisions:
• Whether or not the CPU is to be clocked
• The selection of a clock source
The IDLEN bit of the OSCCON register controls CPU
clocking, while the SCS<1:0> bits of the OSCCON
register select the clock source. The individual modes,
bit settings, clock sources and affected modules are
summarized in
TABLE 19-1:
 2010 Microchip Technology Inc.
Sleep
PRI_RUN
SEC_RUN
RC_RUN
PRI_IDLE
SEC_IDLE
RC_IDLE
Note 1:
Mode
2:
POWER-MANAGED MODES
Selecting Power-Managed Modes
IDLEN reflects its value when the SLEEP instruction is executed.
Includes HFINTOSC and HFINTOSC postscaler, as well as the LFINTOSC source.
Table
IDLEN
POWER-MANAGED MODES
N/A
N/A
N/A
®
0
1
1
1
OSCCON Bits
microcontroller devices, where all
19-1.
(1)
SCS<1:0>
N/A
00
01
1x
00
01
1x
®
microcontroller
Clocked
Clocked
Clocked
CPU
Module Clocking
Off
Off
Off
Off
Preliminary
Peripherals
Clocked
Clocked
Clocked
Clocked
Clocked
Clocked
Off
19.1.1
The SCS<1:0> bits allow the selection of one of three
clock sources for power-managed modes. They are:
• the primary clock, as defined by the FOSC<3:0>
• the secondary clock (the Timer1 oscillator)
• the internal oscillator block
19.1.2
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
Section 2.8 “Clock Switching”
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 of the OSCCON register.
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.
Configuration bits
None – All clocks are disabled
Primary – LP, XT, HS, RC, EC and Internal
Oscillator Block
This is the normal full power execution mode.
Secondary – Timer1 Oscillator
Internal Oscillator Block
Primary – LP, XT, HS, HSPLL, RC, EC
Secondary – Timer1 Oscillator
Internal Oscillator Block
Available Clock and Oscillator Source
PIC18F/LF1XK50
CLOCK SOURCES
ENTERING POWER-MANAGED
MODES
(2)
.
(2)
(2)
for more information.
DS41350E-page 235