Datasheet

 2012 Microchip Technology Inc. DS30684A-page 403
PIC18(L)F2X/45K50
26.5.2 DATA EEPROM
CODE PROTECTION
The entire data EEPROM is protected from external
reads and writes by two bits: CPD and WRTD. CPD
inhibits external reads and writes of data EEPROM.
WRTD inhibits internal and external writes to data
EEPROM. The CPU can always read data EEPROM
under normal operation, regardless of the protection bit
settings.
26.5.3 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 or
an external programmer.
26.6 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.
26.7 In-Circuit Serial Programming
PIC18(L)F2X/45K50 devices 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.
26.8 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 26-6 shows which resources are
required by the background debugger.
TABLE 26-6: DEBUGGER RESOURCES
To use the In-Circuit Debugger function of the
microcontroller, the design must implement In-Circuit
Serial Programming connections to the following pins:
•MCLR
/VPP/RE3
•V
DD
•VSS
•RB7
•RB6
This will interface to the In-Circuit Debugger module
available from Microchip or one of the third party
development tool companies.
26.9 Special ICPORT Features
(44-Pin TQFP Package Only)
Under specific circumstances, the No Connect (NC)
pins of 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.
26.9.1 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 col-
lectively 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 26-7 identifies the functionally equivalent pins for
ICSP and ICD purposes.
TABLE 26-7: EQUIVALENT PINS FOR
LEGACY AND DEDICATED
ICD/ICSP™ PORTS
I/O pins: RB6, RB7
Pin Name
Pin
Type
Pin Function
Legacy
Port
Dedicated
Port
MCLR
/VPP/
RE3
NC/ICRST/
ICV
PP
P Device Reset and
Programming
Enable
RB6/IOCB6/
PGC
NC/ICCK/
ICPGC
I Serial Clock
RB7/IOCB7/
PGD
NC/ICDT/
ICPGD
I/O Serial Data
Legend: I = Input, O = Output, P = Power