PIC16F946-ESLASHMLQTP datasheet(238/330 Pages) MICROCHIP

238 / 330 page

PIC16F913/914/916/917/946

DS41250F-page 236

16.5

Power-Down Mode (Sleep)

The Power-down mode is entered by executing a

SLEEP

instruction.

If the Watchdog Timer is enabled:

• WDT will be cleared but keeps running.

•PD bit in the STATUS register is cleared.

•TO bit is set.

• Oscillator driver is turned off.

• Timer1 oscillator is unaffected

• I/O ports maintain the status they had before

SLEEP

was executed (driving high, low or

high-impedance).

For lowest current consumption in this mode, all I/O

pins should be either at VDD or VSS, with no external

circuitry drawing current from the I/O pin, and the

comparators and CVREF should be disabled. I/O pins

that are high-impedance inputs should be pulled high

or low externally to avoid switching currents caused by

floating inputs. The T0CKI input should also be at VDD

or VSS for lowest current consumption. The

contribution from on-chip pull-ups on PORTB should be

considered.

The MCLR pin must be at a logic high level.

16.5.1

WAKE-UP FROM SLEEP

The device can wake-up from Sleep through one of the

following events:

External Reset input on MCLR pin.

Watchdog Timer wake-up (if WDT was

enabled).

Interrupt from RB0/INT/SEG0 pin, PORTB

change or a peripheral interrupt.

The first event will cause a device Reset. The two latter

events are considered a continuation of program

execution. The TO and PD bits in the STATUS register

can be used to determine the cause of device Reset.

The PD bit, which is set on power-up, is cleared when

Sleep is invoked. TO bit is cleared if WDT wake-up

occurred.

The following peripheral interrupts can wake the device

from Sleep:

TMR1 Interrupt. Timer1 must be operating as an

asynchronous counter.

USART Receive Interrupt (Sync Slave mode

only)

A/D conversion (when A/D clock source is RC)

EEPROM write operation completion

Comparator output changes state

Interrupt-on-change

External Interrupt from INT pin

PLVD Interrupt

LCD Interrupt (if running during Sleep)

Other peripherals cannot generate interrupts since

during Sleep, no on-chip clocks are present.

When the SLEEP instruction is being executed, the next

instruction (PC + 1) is pre-fetched. For the device to

wake-up through an interrupt event, the corresponding

interrupt enable bit must be set (enabled). Wake-up is

regardless of the state of the GIE bit. If the GIE bit is

clear (disabled), the device continues execution at the

instruction after the SLEEP instruction. If the GIE bit is

set (enabled), the device executes the instruction after

the SLEEP instruction, then branches to the interrupt

address (0004h). In cases where the execution of the

instruction following SLEEP is not desirable, the user

should have a NOP after the SLEEP instruction.

The WDT is cleared when the device wakes up from

Sleep, regardless of the source of wake-up.

16.5.2

WAKE-UP USING INTERRUPTS

When global interrupts are disabled (GIE cleared) and

any interrupt source has both its interrupt enable bit

and interrupt flag bit set, one of the following will occur:

• If the interrupt occurs before the execution of a

SLEEP

instruction, the SLEEP instruction will

complete as a NOP. Therefore, the WDT and WDT

prescaler and postscaler (if enabled) will not be

cleared, the TO bit will not be set and the PD bit

will not be cleared.

• If the interrupt occurs during or after the

execution of a SLEEP instruction, the device will

immediately wake-up from Sleep. The SLEEP

instruction will be completely executed before the

wake-up. Therefore, the WDT and WDT prescaler

and postscaler (if enabled) will be cleared, the TO

bit will be set and the PD bit will be cleared.

Note:

It should be noted that a Reset generated

by a WDT time-out does not drive MCLR

pin low.

Note:

If the global interrupts are disabled (GIE is

cleared), but any interrupt source has both

its interrupt enable bit and the correspond-

ing interrupt flag bits set, the device will

immediately wake-up from Sleep. The

SLEEP

instruction is completely executed.

PIC16F946-E/MLQTP Datasheet(PDF) 238 Page - Microchip Technology

PIC16F946-E/MLQTP Datasheet(HTML) 238 Page - Microchip Technology

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