PIC16C765SLASHP datasheet(30/158 Pages) MICROCHIP

30 / 158 page

PIC16C745/765

DS41124A-page 30

Advanced Information

4.5

Indirect Addressing, INDF and FSR

Registers

The INDF register is not a physical register. Addressing

the INDF register will cause indirect addressing.

Indirect addressing is possible by using the INDF reg-

ister. Any instruction using the INDF register actually

accesses the register pointed to by the File Select Reg-

ister, FSR. Reading the INDF register itself indirectly

(FSR = ’0’) will read 00h. Writing to the INDF register

indirectly results in a no-operation (although status bits

may be affected). An effective 9-bit address is obtained

by concatenating the 8-bit FSR register and the IRP bit

(STATUS<7>), as shown in Figure 4-4.

A simple program to clear RAM locations 20h-2Fh

using indirect addressing is shown in Example 4-2.

EXAMPLE 4-2:

INDIRECT ADDRESSING

movlw

0x20

;initialize pointer

movwf

FSR

;to RAM

clrf

INDF

;clear INDF register

incf

FSR,F

;inc pointer

btfss

FSR,4

;all done?

goto

;no clear next

CONTINUE

;yes continue

FIGURE 4-4:

DIRECT/INDIRECT ADDRESSING

Note:

For register file map detail see Figure 4-2.

Data

Memory

Indirect Addressing

Direct Addressing

bank select

location select

RP<1:0>

from opcode

IRP

FSR register

bank select

location select

Bank 0

Bank 1

Bank 2

Bank 3

FFh

80h

7Fh

00h

17Fh

100h

1FFh

180h

PIC16C765/P Datasheet(PDF) 30 Page - Microchip Technology

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