2002 Microchip Technology Inc.
Preliminary
DS30453D-page 47
PIC16C5X
9.3
Power-Down Mode (SLEEP)
A device may be powered down (SLEEP) and later
powered up (Wake-up from SLEEP).
9.3.1
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/VPP pin low.
For lowest current consumption while powered down,
the T0CKI input should be at VDD or VSS and the
MCLR/VPP pin must be at a logic high level
(MCLR = VIH).
9.3.2
WAKE-UP FROM SLEEP
The device can wake up from SLEEP through one of
the following events:
1.
An external RESET input on MCLR/VPP pin.
2.
A Watchdog Timer Time-out Reset (if WDT was
enabled).
Both of these events cause a device RESET. The TO
and PD 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 WDT is cleared when the device wakes from
SLEEP, regardless of the wake-up source.
9.4
Program Verification/Code
Protection
If the code protection bit(s) have not been pro-
grammed, the on-chip program memory can be read
out for verification purposes.
9.5
ID Locations
Four memory locations are designated as ID locations
where the user can store checksum or other code-iden-
tification numbers. These locations are not accessible
during normal execution but are readable and writable
during program/verify.
Use only the lower 4 bits of the ID locations and always
program the upper 8 bits as ’1’s.
Note:
Microchip does not recommend code pro-
tecting windowed devices.
Note:
Microchip will assign a unique pattern
number for QTP and SQTP requests and
for ROM devices. This pattern number will
be unique and traceable to the submitted
code.
