PIC16C5X
7.9
Power-Down Mode (SLEEP)
7.10
Program Verification/Code Protection
A device may be powered down (SLEEP) and later
powered up (Wake-up from SLEEP).
If the code protection bit(s) have not been
programmed, the on-chip program memory can be
read out for verification purposes.
7.9.1
SLEEP
Note: Microchip does not recommend code pro-
The Power-Down mode is entered by executing a
tecting windowed devices.
SLEEPinstruction.
7.11
ID Locations (not implemented on
PIC16C52)
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).
Four memory locations are designated as ID locations
where the user can store checksum or other
code-identification numbers. These locations are not
accessible during normal execution but are readable
and writable during program/verify.
It should be noted that a RESET generated by a WDT
time-out does not drive the MCLR/VPP pin low.
Use only the lower 4 bits of the ID locations and
always program the upper 8 bits as '1's.
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.
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.
7.9.2
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 SLEEPis invoked.
The WDT is cleared when the device wakes from
sleep, regardless of the wake-up source.
DS30453B-page 42
Preliminary
1998 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
