PIC18F2X1X Datasheet, PDF (257/380 Pages) Microchip Technology – 28/40/44-PIN FLASH MICROCONTROLLERS WITH 10-BIT A/D AND NANO WATT TECHNOLOGY

PIC18F2X1X/4X1X
FIGURE 22-10:
EXTERNAL BLOCK TABLE READ (EBTRn) ALLOWED
(48-KBYTE AND 64-KBYTE DEVICES)
Register Values
TBLPTR = 0008FFh
Program Memory
000000h
0007FFh
000800h
Configuration Bit Settings
WRTB, EBTRB = 11
WRT0, EBTR0 = 10
PC = 001FFEh
TBLRD*
003FFFh
004000h
007FFFh
008000h
00BFFFh
00C000h
00FFFFh
WRT1, EBTR1 = 11
WRT2, EBTR2 = 11
WRT3, EBTR3 = 11
Results: Table reads permitted within Blockn, even when EBTRBn = 0.
TABLAT register returns the value of the data at the location TBLPTR.
22.5.2 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 or
an external programmer.
22.6 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 instruction; during
program/verify these locations are readable and
writable. The ID locations can be read when the device
is code-protected.
22.7 In-Circuit Serial Programming
PIC18F2X1X/4X1X 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.
22.8 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 22-4 shows which resources are
required by the background debugger.
TABLE 22-4: DEBUGGER RESOURCES
I/O pins:
RB6, RB7
Stack:
2 levels
Program Memory:
512 bytes
Data Memory:
10 bytes
To use the In-Circuit Debugger function of the micro-
controller, 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.
 2004 Microchip Technology Inc.
Preliminary
DS39636A-page 255