PIC16F627A_05 Datasheet, PDF (114/180 Pages) Microchip Technology – Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F627A/628A/648A
14.11 In-Circuit Serial Programming™
(ICSP™)
The PIC16F627A/628A/648A 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 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 custom firmware to be programmed.
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 “PIC16F627A/
628A/648A EEPROM Memory Programming
Specification” (DS41196) for details. RB6 becomes the
programming clock and RB7 becomes the programming
data. Both RB6 and RB7 are Schmitt Trigger inputs in
this mode.
After Reset, to place the device into Programming/Verify
mode, the Program Counter (PC) is at location 00h. 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 “PIC16F627A/628A/648A
EEPROM Memory Programming Specification”
(DS41196).
A typical In-Circuit Serial Programming connection is
shown in Figure 14-18.
FIGURE 14-18:
TYPICAL IN-CIRCUIT
SERIAL PROGRAMMING
CONNECTION
External
Connector
Signals
+5V
0V
VPP
CLK
Data I/O
To Normal
Connections
PIC16F627A/628A/648A
VDD
VSS
RA5/MCLR/VPP
RB6/PGC
RB7/PGD
14.12 Low-Voltage Programming
The LVP bit of the Configuration Word, enables the low-
voltage programming. This mode allows the
microcontroller to be programmed via ICSP using only
a 5V source. This mode removes the requirement of
VIHH to be placed on the MCLR pin. The LVP bit is
normally erased to ‘1’ which enables the low-voltage
programming. In this mode, the RB4/PGM pin is
dedicated to the programming function and ceases to
be a general purpose I/O pin. The device will enter
Programming mode when a ‘1’ is placed on the RB4/
PGM pin. The High-Voltage Programming mode is still
available by placing VIHH on the MCLR pin.
Note 1: While in this mode, the RB4 pin can no
longer be used as a general purpose I/O
pin.
2: VDD must be 5.0V +10% during erase
operations.
If Low-Voltage Programming mode is not used, the
LVP bit should be programmed to a ‘0’ so that RB4/
PGM becomes a digital I/O pin. To program the device,
VIHH must be placed onto MCLR during programming.
The LVP bit may only be programmed when program-
ming is entered with VIHH on MCLR. The LVP bit
cannot be programmed when programming is entered
with RB4/PGM.
It should be noted, that once the LVP bit is programmed
to ‘0’, only High-Voltage Programming mode can be
used to program the device.
VDD
To Normal
Connections
DS40044D-page 112
© 2005 Microchip Technology Inc.