PIC16C926 Microchip Technology Inc., PIC16C926 Datasheet - Page 113

• Manufacturer Part Number: PIC16C926
• Description: 64/68-pin Cmos Microcontrollers With Lcd Driver
• Manufacturer: Microchip Technology Inc.

12.8
Power-down mode is entered by executing a SLEEP
instruction.
If enabled, the Watchdog Timer will be cleared but
keeps running, the PD bit (STATUS<3>) is cleared, the
TO (STATUS<4>) bit is set, and the oscillator driver is
turned off. The I/O ports maintain the status they had,
before the SLEEP instruction was executed (driving
high, low, or hi-impedance).
For lowest current consumption in this mode, place all
I/O pins at either V
cuitry is drawing current from the I/O pin, power-down
the A/D, disable external clocks. Pull all I/O pins that
are hi-impedance inputs, high or low externally, to avoid
switching currents caused by floating inputs. The
T0CKI input should also be at V
current consumption. The contribution from on-chip
pull-ups on PORTB should also be considered.
The MCLR pin must be at a logic high level (V
12.8.1
The device can wake-up from SLEEP through one of
the following events:
1.
2.
3.
External MCLR Reset will cause a device RESET. All
other events are considered a continuation of program
execution and cause a “wake-up”. 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. The TO bit
is cleared if a WDT time-out occurred (and caused
wake-up).
The following peripheral interrupts can wake the device
from SLEEP:
1.
2.
3.
4.
5.
6.
7.
2001 Microchip Technology Inc.
External RESET input on MCLR pin.
Watchdog Timer Wake-up (if WDT was
enabled).
Interrupt from RB0/INT pin, RB port change, or
peripheral interrupt.
TMR1 interrupt. Timer1 must be operating as an
asynchronous counter.
SSP (START/STOP) bit detect interrupt.
SSP transmit or receive in Slave mode
(SPI/I
CCP Capture mode interrupt.
A/D conversion (when A/D clock source is RC).
Special event trigger (Timer1 in Asynchronous
mode using an external clock).
LCD module.
Power-down Mode (SLEEP)
2
C).
WAKE-UP FROM SLEEP
DD
, or V
SS
, ensure no external cir-
DD
or V
SS
for lowest
IHMC
).
Preliminary
Other peripherals can not generate interrupts since
during SLEEP, no on-chip Q 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 and then branches to the inter-
rupt 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.
12.8.2
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
• If the interrupt occurs during or after the execu-
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 instruc-
tion should be executed before a SLEEP instruction.
SLEEP instruction, the SLEEP instruction will com-
plete as a NOP. Therefore, the WDT and WDT
postscaler will not be cleared, the TO bit will not
be set and PD bits will not be cleared.
tion of a SLEEP instruction, the device will imme-
diately wake-up from SLEEP. The SLEEP
instruction will be completely executed before the
wake-up. Therefore, the WDT and WDT
postscaler will be cleared, the TO bit will be set
and the PD bit will be cleared.
WAKE-UP USING INTERRUPTS
PIC16C925/926
DS39544A-page 111