PIC18F2221 MICROCHIP [Microchip Technology], PIC18F2221 Datasheet - Page 273

• Manufacturer Part Number: PIC18F2221
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

23.5.2
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.
23.5.3
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.
23.6
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.
23.7
PIC18F4321 family 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.
23.8
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
this feature enabled, some resources are not available
for general use. Table 23-4 shows which resources are
required by the background debugger.
TABLE 23-4:
© 2007 Microchip Technology Inc.
I/O pins:
Stack:
Program Memory:
Data Memory:
ID Locations
In-Circuit Debugger
In-Circuit Serial Programming
DATA EEPROM
CODE PROTECTION
CONFIGURATION REGISTER
PROTECTION
®
DEBUGGER RESOURCES
IDE. When the microcontroller has
RB6, RB7
2 levels
512 bytes
10 bytes
Preliminary
To use the In-Circuit Debugger function of the micro-
controller, the design must implement In-Circuit Serial
Programming connections to MCLR/V
V
Debugger module available from Microchip or one of
the third party development tool companies.
23.9
Under specific circumstances, the No Connect (NC)
pins of PIC18F4221/4321 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.
23.9.1
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 23-5 identifies the functionally equivalent pins for
ICSP and ICD purposes.
TABLE 23-5:
MCLR/V
RE3
RB6/KBI2/
PGC
RB7/KBI3/
PGD
Legend:
PIC18F4321 FAMILY
SS
Legacy
, RB7 and RB6. This will interface to the In-Circuit
Port
Pin Name
PP
Special ICPORT Features
(44-Pin TQFP Packages Only)
/
I = Input, O = Output, P = Power
DEDICATED ICD/ICSP PORT
NC/ICRST/
ICV
NC/ICCK/
ICPGC
NC/ICDT/
ICPGD
Dedicated
PP
EQUIVALENT PINS FOR
LEGACY AND DEDICATED
ICD/ICSP™ PORTS
Port
Type
Pin
I/O
P
I
Device Reset and
Programming
Enable
Serial Clock
Serial Data
DS39689E-page 271
Pin Function
PP
/RE3, V
DD
,