PIC16F753 Datasheet, PDF (177/238 Pages) Microchip Technology – 14/16-Pin, Flash-Based 8-Bit CMOS Microcontrollers

19.7 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
• 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,
DAC and FVR 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 PORTA should be considered.
The MCLR pin must be at a logic high level.
Note:
It should be noted that a Reset generated
by a WDT time-out does not drive MCLR
pin low.
19.7.1 WAKE-UP FROM SLEEP
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.
3. Interrupt from INT pin.
4. Interrupt-On-Change input change.
5. Peripheral interrupt.
The first event will cause a device Reset. The other
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. Timer1 interrupt. Timer1 must be operating as
an asynchronous counter.
2. CCP Capture mode interrupt.
3. A/D conversion (when A/D clock source is RC).
4. Comparator output changes state.
5. Interrupt-on-change.
6. External Interrupt from INT pin.
Other peripherals cannot generate interrupts since
during Sleep, no on-chip clocks are present.
PIC16F753/HV753
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.
Note:
If the global interrupts are disabled (GIE is
cleared) and 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 WDT is cleared when the device wakes up from
Sleep, regardless of the source of wake-up.
19.7.2 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 is executed. 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.
Even if the flag bits were checked before executing a
SLEEP instruction, it may be possible for flag bits to
become set before the SLEEP instruction completes. To
determine whether a SLEEP instruction executed, test
the PD bit. If the PD bit is set, the SLEEP instruction
was executed as a NOP.
To ensure that the WDT is cleared, a CLRWDT instruction
should be executed before a SLEEP instruction. See
Figure 19-10 for more details.
 2013 Microchip Technology Inc.
Preliminary
DS40001709A-page 177