PIC18F2450 Datasheet, PDF (211/320 Pages) Microchip Technology – 28/40/44-Pin, High-Performance, 12 MIPS, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

18.5.2 CONFIGURATION REGISTER
PROTECTION
The Configuration registers can be write-protected.
The WRTC bit controls protection of the Configuration
registers. In normal execution mode, the WRTC bit is
readable only. WRTC can only be written via ICSP
operation or an external programmer.
18.6 ID Locations
Eight memory locations (200000h-200007h) are
designated as ID locations, where the user can store
checksum or other code identification numbers. These
locations are both readable and writable during normal
execution through the TBLRD and TBLWT instructions
or during program/verify. The ID locations can be read
when the device is code-protected.
18.7 In-Circuit Serial Programming
PIC18F2450/4450 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.
18.8 In-Circuit Debugger
When the DEBUG Configuration bit is programmed to
a ‘0’, the In-Circuit Debugger functionality is enabled.
This function allows simple debugging functions when
used with MPLAB^® IDE. When the microcontroller has
this feature enabled, some resources are not available
for general use. Table 18-4 shows which resources are
required by the background debugger.
TABLE 18-4: DEBUGGER RESOURCES
I/O pins:
RB6, RB7
Stack:
2 levels
Program Memory:
512 bytes
Data Memory:
10 bytes
PIC18F2450/4450
To use the In-Circuit Debugger function of the
microcontroller, the design must implement In-Circuit
Serial Programming connections to MCLR/VPP/RE3,
VDD, VSS, RB7 and RB6. This will interface to the
In-Circuit Debugger module available from Microchip
or one of the third party development tool companies.
18.9 Special ICPORT Features
(Designated Packages Only)
Under specific circumstances, the No Connect (NC)
pins of PIC18F4450 devices in 44-pin TQFP packages
can provide additional functionality. These features are
controlled by device Configuration bits and are
available only in this package type and pin count.
18.9.1 DEDICATED ICD/ICSP PORT
The 44-pin TQFP devices can use NC pins to provide an
alternate port for In-Circuit Debugging (ICD) and In-
Circuit Serial Programming (ICSP). These pins are
collectively known as the dedicated ICSP/ICD port, since
they are not shared with any other function of the device.
When implemented, the dedicated port activates three
NC pins to provide an alternate device Reset, data and
clock ports. None of these ports overlap with standard
I/O pins, making the I/O pins available to the user’s
application.
The dedicated ICSP/ICD port is enabled by setting the
ICPRT Configuration bit. The port functions the same
way as the legacy ICSP/ICD port on RB6/RB7.
Table 18-5 identifies the functionally equivalent pins for
ICSP and ICD purposes.
TABLE 18-5: EQUIVALENT PINS FOR
LEGACY AND DEDICATED
ICD/ICSP™ PORTS
Pin Name
Legacy
Port
Dedicated
Port
Pin
Type
Pin Function
MCLR/VPP/ NC/ICRST/
RE3
ICVPP
P Device Reset and
Programming
Enable
RB6/KBI2/ NC/ICCK/
PGC
ICPGC
I Serial Clock
RB7/KBI3/ NC/ICDT/
PGD
ICPGD
I/O Serial Data
Legend: I = Input, O = Output, P = Power
© 2006 Microchip Technology Inc.
Advance Information
DS39760A-page 209