PIC18LF4331 datasheet(77/392 Pages) MICROCHIP

77 / 392 page

 2010 Microchip Technology Inc.

DS39616D-page 77

PIC18F2331/2431/4331/4431

The PLUSW register can be used to implement a form

of Indexed Addressing in the data memory space. By

manipulating the value in the W register, users can

reach addresses that are fixed offsets from pointer

addresses. In some applications, this can be used to

implement some powerful program control structure,

such as software stacks, inside of data memory.

6.7.3.3

Operations by FSRs on FSRs

Indirect Addressing operations that target other FSRs or

virtual registers represent special cases. For example,

using an FSR to point to one of the virtual registers will

not result in successful operations. As a specific case,

assume that FSR0H:FSR0L contain FE7h, the address

of INDF1. Attempts to read the value of the INDF1 using

INDF0 as an operand will return 00h. Attempts to write

to INDF1 using INDF0 as the operand will result in a NOP.

On the other hand, using the virtual registers to write to

an FSR pair may not occur as planned. In these cases,

the value will be written to the FSR pair but without any

incrementing or decrementing. Thus, writing to INDF2

or POSTDEC2 will write the same value to the

FSR2H:FSR2L.

Since the FSRs are physical registers mapped in the

SFR space, they can be manipulated through all direct

operations. Users should proceed cautiously when

working on these registers, particularly if their code

uses Indirect Addressing.

Similarly, operations by Indirect Addressing are gener-

ally permitted on all other SFRs. Users should exercise

the appropriate caution that they do not inadvertently

change settings that might affect the operation of the

device.

PIC18LF4331 Datasheet(PDF) 77 Page - Microchip Technology