PIC16F5X
8.3
Power-Down Mode (Sleep)
8.5
User ID Locations
A device may be powered down (Sleep) and later
powered up (wake-up from Sleep).
Four memory locations are designated as user ID loca-
tions 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.
8.3.1
SLEEP
The Power-down mode is entered by executing a
SLEEPinstruction.
Use only the lower 4 bits of the user ID locations and
always program the upper 8 bits as ‘1’s.
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 high-impedance).
Note:
Microchip will assign a unique pattern
number for QTP and SQTP requests. This
pattern number will be unique and trace-
able to the submitted code.
It should be noted that a Reset generated by a WDT
time-out does not drive the MCLR/VPP pin low.
8.6
In-Circuit Serial Programming™
(ICSP™)
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).
The PIC16F5X microcontrollers can be serially
programmed while in the end application circuit. This is
simply done with two lines for clock and data, and three
other lines for power, ground and programming
voltage. This allows customers to manufacture boards
with unprogrammed devices and then program the
microcontroller just before shipping the product. Thus,
the most recent firmware or custom firmware can be
programmed.
8.3.2
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).
The device is placed into a Program/Verify mode by
holding the RB6 and RB7 pins low while raising the
MCLR (VPP) pin from VIL to VIHH (see programming
specification). RB6 becomes the programming clock
and RB7 becomes the programming data. Both RB6
and RB7 are Schmitt Trigger inputs in this mode.
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.
A 6-bit command is then supplied to the device.
Depending on the command, 14 bits of program data
are then supplied to or from the device, depending if
the command was a Load or a Read. For complete
details of serial programming, please refer to the
respective Programming Specifications: “PIC16F54
Memory Programming Specification” (DS41207),
“PIC16F57 Memory Programming Specification”
(DS41208), and “PIC16F59 Memory Programming
Specification” (DS41243).
The WDT is cleared when the device wakes from
Sleep, regardless of the wake-up source.
8.4
Program Verification/Code
Protection
If the code protection bit has not been programmed, the
on-chip program memory can be read out for
verification purposes.
A typical In-Circuit Serial Programming connection is
shown in Figure 8-1.
Once code protection is enabled, all program memory
locations above 0x3F read all ‘0’s. Program memory
locations 0x00-0x3F are always unprotected. The user
ID locations and the Configuration Word read out in an
unprotected fashion. It is possible to program the user
ID locations and the Configuration Word after code
protect is enabled.
© 2007 Microchip Technology Inc.
DS41213D-page 39
MICROCHIP [ MICROCHIP ]
