Microchip Technology AC164112 Data Sheet

© 2009 Microchip Technology Inc.

DS41341E-page 193

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 of the STATUS register is cleared.

• TO bit of the STATUS register 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 V

DD

 or V

SS

, with no external

circuitry drawing current from the I/O pin. I/O pins that
are high-impedance inputs should be pulled high or low
externally to avoid switching currents caused by float-
ing inputs. The T0CKI input should also be at V

DD

 or

V

SS

 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 when
external MCLR is enabled.      

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

1.

External Reset input on MCLR pin.

2.

Watchdog Timer wake-up (if WDT was
enabled).

3.

Interrupt from RB0/INT 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:

1.

TMR1 Interrupt. Timer1 must be operating as an
asynchronous counter.

2.

USART Receive Interrupt (Synchronous Slave
mode only)

3.

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

4.

Interrupt-on-change

5.

External Interrupt from INT pin

6.

Capture event on CCP1 or CCP2

7.

SSP Interrupt in SPI or I

2

C Slave mode

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 prefetched. 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.

A Reset generated by a WDT time-out
does not drive MCLR pin low.

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.