PIC18F1220 datasheet(21/310 Pages) MICROCHIP

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 2004 Microchip Technology Inc.

DS39605C-page 19

PIC18F1220/1320

3.0

POWER MANAGED MODES

The PIC18F1220/1320 devices offer a total of six oper-

ating modes for more efficient power management

(see Table 3-1). These 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:

• Sleep mode

• Idle modes

• Run modes

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 INTOSC multiplexer);

the Sleep mode does not use a clock source.

The clock switching feature offered in other PIC18

devices (i.e., using the Timer1 oscillator in place of the

primary oscillator) and the Sleep mode offered by all

PICmicro® devices (where all system clocks are

stopped) are both offered in the PIC18F1220/1320

devices (SEC_RUN and Sleep modes, respectively).

However, additional power managed modes are avail-

able that allow the user greater flexibility in determining

what portions of the device are operating. The power

managed modes are event driven; that is, some

specific event must occur for the device to enter or

(more particularly) exit these operating modes.

For PIC18F1220/1320 devices, the power managed

modes are invoked by using the existing SLEEP

instruction. All modes exit to PRI_RUN mode when trig-

gered by an interrupt, a Reset or a WDT time-out

(PRI_RUN mode is the normal full power execution

mode; the CPU and peripherals are clocked by the pri-

mary oscillator source). In addition, power managed

Run modes may also exit to Sleep mode, or their

corresponding Idle mode.

3.1

Selecting Power Managed Modes

Selecting a power managed mode requires deciding if

the CPU is to be clocked or not and selecting a clock

source. The IDLEN bit controls CPU clocking, while the

SCS1:SCS0 bits select a clock source. The individual

modes, bit settings, clock sources and affected

modules are summarized in Table 3-1.

3.1.1

CLOCK SOURCES

The clock source is selected by setting the SCS bits of

the OSCCON register (Register 2-2). Three clock

sources are available for use in power managed Idle

modes: the primary clock (as configured in Configuration

and the internal oscillator block. The secondary and

internal oscillator block sources are available for the

power managed modes (PRI_RUN mode is the normal

full power execution mode; the CPU and peripherals are

clocked by the primary oscillator source).

TABLE 3-1:

POWER MANAGED MODES

Mode

OSCCON Bits

Module Clocking

Available Clock and Oscillator Source

IDLEN

<7>

SCS1:SCS0

<1:0>

CPU

Peripherals

Sleep

000

Off

None – All clocks are disabled

PRI_RUN

000

Clocked

Primary – LP, XT, HS, HSPLL, RC, EC, INTRC(1)

This is the normal full power execution mode.

SEC_RUN

001

Clocked

Secondary – Timer1 Oscillator

RC_RUN

01x

Clocked

Internal Oscillator Block(1)

PRI_IDLE

100

Off

Clocked

Primary – LP, XT, HS, HSPLL, RC, EC

SEC_IDLE

101

Off

Clocked

Secondary – Timer1 Oscillator

RC_IDLE

11x

Off

Clocked

Internal Oscillator Block(1)

Note 1:

Includes INTOSC and INTOSC postscaler, as well as the INTRC source.

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