PIC16C55X(A)
7.9
Code Protection
7.11
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.
The PIC16C55X(A) 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.
Note: Microchip does not recommend code
protecting windowed devices.
7.10
ID Locations
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.
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 PIC16C6X/7X
Programming Specifications (Literature #DS30228).
A typical in-circuit serial programming connection is
shown in Figure 7-17.
FIGURE 7-17: TYPICAL IN-CIRCUIT SERIAL
PROGRAMMING
CONNECTION
To Normal
Connections
External
Connector
Signals
PIC16C55X(A)
+5V
0V
VDD
VSS
VPP
MCLR/VPP
RB6
RB7
CLK
Data I/O
VDD
To Normal
Connections
DS40143B-page 50
Preliminary
1997 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
