RFPIC12C509AG Datasheet, PDF (55/104 Pages) Microchip Technology – 18/20-Pin 8-Bit CMOS Microcontroller with UHF ASK/FSK Transmitter

rfPIC12C509AG/509AF
8.8 Power-Down Mode (SLEEP)
The SLEEP mode is designed to offer a very low cur-
rent power-down mode. The user can wake-up from
SLEEP through a change on input pins or through a
Watchdog Timer time-out. Several oscillator options
are also made available to allow the part to fit the appli-
cation, including an internal 4 MHz oscillator. The
EXTRC oscillator option saves system cost while the
LP crystal option saves power. A set of configuration
bits are used to select various options.
A device may be powered down (SLEEP) and later
powered up (Wake-up from SLEEP).
8.8.1 SLEEP
The Power-down mode is entered by executing a
SLEEP instruction.
If enabled, the Watchdog Timer will be cleared but
keeps running, the TO bit (STATUS<4>) is set, the PD
bit (STATUS<3>) is cleared and the oscillator driver is
turned off. The I/O ports maintain the status they had
before the SLEEP instruction was executed (driving
high, driving low, or hi-impedance).
It should be noted that a RESET generated by a WDT
time-out does not drive the MCLR pin low.
For lowest current consumption while powered down,
the T0CKI input should be at VDD or VSS and the GP3/
MCLR/VPP pin must be at a logic high level (VIHMC) if
MCLR is enabled.
8.8.2 WAKE-UP FROM SLEEP
The device can wake-up from SLEEP through one of
the following events:
1. An external RESET input on GP3/MCLR/VPP
pin, when configured as MCLR.
2. A Watchdog Timer time-out Reset (if WDT was
enabled).
3. A change on input pin GP0, GP1, or GP3/
MCLR/VPP when wake-up on change is
enabled.
These events cause a device RESET. The TO, PD, and
GPWUF bits can be used to determine the cause of
device RESET. The TO bit is cleared if a WDT time-out
occurred (and caused wake-up). The PD bit, which is
set on power-up, is cleared when SLEEP is invoked.
The GPWUF bit indicates a change in state while in
SLEEP at pins GP0, GP1, or GP3 (since the last time
there was a file or bit operation on GP port).
Caution: Right before entering SLEEP, read the
input pins. When in SLEEP, wake up
occurs when the values at the pins change
from the state they were in at the last read-
ing. If a wake-up on change occurs and
the pins are not read before reentering
SLEEP, a wake up will occur immediately
even if no pins change while in SLEEP
mode.
The WDT is cleared when the device wakes from
sleep, regardless of the wake-up source.
© 2001 Microchip Technology Inc.
Preliminary
DS70031A-page 53