PIC16C62B Microchip Technology, PIC16C62B Datasheet - Page 67

• Manufacturer Part Number: PIC16C62B
• Description: 28-Pin 8-Bit CMOS Microcontrollers
• Manufacturer: Microchip Technology

10.13
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 be considered.
The MCLR pin must be at a logic high level (V
10.13.1 WAKE-UP FROM SLEEP
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.
1998 Microchip Technology Inc.
External reset input on MCLR pin.
Watchdog Timer Wake-up
enabled).
Interrupt from INT pin, RB port change, or some
Peripheral Interrupts.
TMR1 interrupt. Timer1 must be operating as
an asynchronous counter.
CCP capture mode interrupt.
Special event trigger (Timer1 in asynchronous
mode using an external clock).
SSP (Start/Stop) bit detect interrupt.
SSP transmit or receive in slave mode (SPI/I
USART RX or TX (synchronous slave mode).
Power-down Mode (SLEEP)
DD
, or V
SS
, ensure no external cir-
DD
(if WDT
or V
SS
for lowest
IHMC
2
was
C).
).
Preliminary
Other peripherals cannot generate interrupts since dur-
ing 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 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.
10.13.2 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
• 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.
be set and PD bits will not be cleared.
tion of a SLEEP instruction, the device will imme-
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
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.
PIC16C62B/72A
DS35008A-page 67