PIC16F62X
14.10 Code Protection
FIGURE 14-20: TYPICAL IN-CIRCUIT SERIAL
PROGRAMMING
If the code protection bit(s) have not been
programmed, the on-chip program memory can be
read out for verification purposes.
CONNECTION
To Normal
Connections
Note: The entire data EEPROM and FLASH
program memory will be erased when the
code protection is turned off. The INTRC
calibration data is not erased.
External
Connector
Signals
PIC16F62X
+5V
0V
VDD
VSS
14.11 ID Locations
VPP
RA5/MCLR/THV
Four memory locations (2000h-2003h) 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. Only the
least significant 4 bits of the ID locations are used.
RB6
RB7
CLK
Data I/O
VDD
14.12 In-Circuit Serial Programming
To Normal
Connections
The PIC16F62X 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 a custom
firmware to be programmed.
14.13 Low Voltage Programming
The LVP bit of the configuration word, enables the low
voltage programming. This mode allows the microcon-
troller 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 program-
ming. 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
HV programming mode is still available by placing VIHH
on the MCLR pin.
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.
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 the Programming
Specifications.
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/pro-
gram operations while in low voltage pro-
gramming mode.
A typical in-circuit serial programming connection is
shown in Figure 14-20.
If Low-voltage programming mode is not used, the LVP
bit can be programmed to a ’0’ and 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 programming 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 the high voltage programming mode is avail-
able and only high voltage programming mode can be
used to program the device.
DS40300B-page 112
Preliminary
1999 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
