PIC16F872_06 Datasheet, PDF (104/168 Pages) Microchip Technology – 28-Pin, 8-Bit CMOS Flash Microcontroller with 10-Bit A/D

PIC16F872
11.17 In-Circuit Serial Programming
PIC16F872 microcontrollers can be serially pro-
grammed 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 the programming
voltage. This allows customers to manufacture boards
with unprogrammed devices, and then program the
microcontroller just before shipping the product. This
also allows the most recent firmware or a custom firm-
ware to be programmed.
When using ICSP, the part must be supplied 4.5V to
5.5V if a bulk erase will be executed. This includes
reprogramming of the code protect, both from an on-
state to off-state. For all other cases of ICSP, the part
may be programmed at the normal operating voltages.
This means calibration values, unique user IDs or user
code can be reprogrammed or added.
For complete details of serial programming, please
refer to the EEPROM Memory Programming Specifica-
tion for the PIC16F87X (DS39025).
11.18 Low Voltage ICSP Programming
The LVP bit of the configuration word enables low volt-
age ICSP programming. This mode allows the micro-
controller to be programmed via ICSP, using a VDD
source in the operating voltage range. This only means
that VPP does not have to be brought to VIHH, but can
instead be left at the normal operating voltage. In this
mode, the RB3/PGM pin is dedicated to the program-
ming function and ceases to be a general purpose I/O
pin. During programming, VDD is applied to the MCLR
pin. To enter Programming mode, VDD must be applied
to the RB3/PGM pin, provided the LVP bit is set. The
LVP bit defaults to on (‘1’) from the factory.
Note 1: The High Voltage Programming mode is
always available, regardless of the state
of the LVP bit, by applying VIHH to the
MCLR pin.
2: While in low voltage ICSP mode, the RB3
pin can no longer be used as a general
purpose I/O pin.
3: When using low voltage ICSP program-
ming (LVP) and the pull-ups on PORTB
are enabled, bit 3 in the TRISB register
must be cleared to disable the pull-up on
RB3 and ensure the proper operation of
the device.
If Low Voltage Programming mode is not used, the LVP
bit can be programmed to a '0' and RB3/PGM becomes
a digital I/O pin. However, the LVP bit may only be pro-
grammed when programming is entered with VIHH on
MCLR. The LVP bit can only be charged when using
high voltage on MCLR.
It should be noted that once the LVP bit is programmed
to 0, only the High Voltage Programming mode is avail-
able and only High Voltage Programming mode can be
used to program the device.
When using low voltage ICSP, the part must be sup-
plied 4.5V to 5.5V if a bulk erase will be executed. This
includes reprogramming of the code protect bits from
an on-state to off-state. For all other cases of low volt-
age ICSP, the part may be programmed at the normal
operating voltage. This means calibration values,
unique user IDs, or user code can be reprogrammed or
added.
DS30221C-page 102
© 2006 Microchip Technology Inc.