Microchip Technology MA160014 Data Sheet

DS41412F-page 94

 2010-2012 Microchip Technology Inc.

5.7.3

MAPPING THE ACCESS BANK IN 
INDEXED LITERAL OFFSET MODE

The use of Indexed Literal Offset Addressing mode
effectively changes how the first 96 locations of Access
RAM (00h to 5Fh) are mapped. Rather than containing
just the contents of the bottom section of Bank 0, this
mode maps the contents from a user defined “window”
that can be located anywhere in the data memory
space. The value of FSR2 establishes the lower bound-
ary of the addresses mapped into the window, while the
upper boundary is defined by FSR2 plus 95 (5Fh).
Addresses in the Access RAM above 5Fh are mapped
as previously described (see 

). An example of Access Bank remapping in this

addressing mode is shown in 

Remapping of the Access Bank applies only to opera-
tions using the Indexed Literal Offset mode. Operations
that use the BSR (Access RAM bit is ‘1’) will continue
to use direct addressing as before. 

Enabling the extended instruction set adds eight
additional commands to the existing PIC18 instruction
set. These instructions are executed as described in

000h

100h

200h

F60h

F00h

FFFh

Bank 1

Bank 15

Bank 2

through

Bank 14

SFRs

ADDWF f, d, a

FSR2H:FSR2L = 120h

Locations in the region
from the FSR2 pointer
(120h) to the pointer plus
05Fh (17Fh) are mapped
to the bottom of the
Access RAM (000h-05Fh).

Special File Registers at
F60h through FFFh are
mapped to 60h through
FFh, as usual.

Bank 0 addresses below
5Fh can still be addressed
by using the BSR.

00h

60h

FFh

Bank 0

Window

120h

17Fh

5Fh

Bank 1