PIC24FJ256GB108-I Datasheet, PDF (287/352 Pages) Microchip Technology – 64/80/100-Pin, 16-Bit Flash Microcontrollers with USB On-The-Go (OTG)

PIC24FJ256GB110 FAMILY
26.0 SPECIAL FEATURES
Note:
This data sheet summarizes the features
of this group of PIC24F devices. It is not
intended to be a comprehensive reference
source. For more information, refer to the
following sections of the “PIC24F Family
Reference Manual”:
• Section 9. “Watchdog Timer (WDT)”
(DS39697)
• Section 32. “High-Level Device
Integration” (DS39719)
• Section 33. “Programming and
Diagnostics” (DS39716)
PIC24FJ256GB110 family devices include several
features intended to maximize application flexibility and
reliability, and minimize cost through elimination of
external components. These are:
• Flexible Configuration
• Watchdog Timer (WDT)
• Code Protection
• JTAG Boundary Scan Interface
• In-Circuit Serial Programming
• In-Circuit Emulation
26.1 Configuration Bits
The Configuration bits can be programmed (read as ‘0’),
or left unprogrammed (read as ‘1’), to select various
device configurations. These bits are mapped starting at
program memory location F80000h. A detailed explana-
tion of the various bit functions is provided in
Register 26-1 through Register 26-5.
Note that address F80000h is beyond the user program
memory space. In fact, it belongs to the configuration
memory space (800000h-FFFFFFh) which can only be
accessed using table reads and table writes.
26.1.1
CONSIDERATIONS FOR
CONFIGURING PIC24FJ256GB110
FAMILY DEVICES
In PIC24FJ256GB110 family devices, the configuration
bytes are implemented as volatile memory. This means
that configuration data must be programmed each time
the device is powered up. Configuration data is stored
in the three words at the top of the on-chip program
memory space, known as the Flash Configuration
Words. Their specific locations are shown in
Table 26-1. These are packed representations of the
actual device Configuration bits, whose actual
locations are distributed among several locations in
configuration space. The configuration data is automat-
ically loaded from the Flash Configuration Words to the
proper Configuration registers during device Resets.
Note: Configuration data is reloaded on all types
of device Resets.
When creating applications for these devices, users
should always specifically allocate the location of the
Flash Configuration Word for configuration data. This is
to make certain that program code is not stored in this
address when the code is compiled.
The upper byte of all Flash Configuration Words in pro-
gram memory should always be ‘1111 1111’. This
makes them appear to be NOP instructions in the
remote event that their locations are ever executed by
accident. Since Configuration bits are not implemented
in the corresponding locations, writing ‘1’s to these
locations has no effect on device operation.
Note:
Performing a page erase operation on the
last page of program memory clears the
Flash Configuration Words, enabling code
protection as a result. Therefore, users
should avoid performing page erase
operations on the last page of program
memory.
TABLE 26-1: FLASH CONFIGURATION WORD LOCATIONS FOR PIC24FJ256GB110 FAMILY
DEVICES
Device
Configuration Word Addresses
1
2
3
PIC24FJ64GB1
PIC24FJ128GB1
PIC24FJ192GB1
PIC24FJ256GB1
ABFEh
157FEh
20BFEh
2ABFEh
ABFCh
157FC
20BFC
2ABFC
ABFAh
157FA
20BFA
2ABFA
 2009 Microchip Technology Inc.
DS39897C-page 287