Datasheet

 2010-2016 Microchip Technology Inc. DS40001412G-page 89
PIC18(L)F2X/4XK22
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 Section 5.4.2 “Access
Bank”). An example of Access Bank remapping in this
addressing mode is shown in Figure 5-12.
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.
5.8 PIC18 Instruction Execution and
the Extended Instruction Set
Enabling the extended instruction set adds eight
additional commands to the existing PIC18 instruction
set. These instructions are executed as described in
Section 25.2 “Extended Instruction Set”.
FIGURE 5-12: REMAPPING THE ACCESS BANK WITH INDEXED LITERAL OFFSET
ADDRESSING
Data Memory
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.
Access Bank
00h
60h
FFh
SFRs
Bank 1 “Window”
Bank 0
Window
Example Situation:
120h
17Fh
5Fh
Bank 1