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PIC12F629/675

2.4 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

ally accesses data pointed to by the File Select register

(FSR). Reading INDF itself indirectly will produce 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 2-4.

A simple program to clear RAM location 20h-2Fh using

indirect addressing is shown in Example 2-1.

EXAMPLE 2-1: INDIRECT ADDRESSING

FIGURE 2-4: DIRECT/INDIRECT ADDRESSING PIC12F629/675

movlw 0x20 ;initialize pointer

movwf FSR ;to RAM

NEXT clrf INDF ;clear INDF register

incf FSR ;inc pointer

btfss FSR,4 ;all done?

goto NEXT ;no clear next

CONTINUE ;yes continue

For memory map detail see Figure 2-2.

Note 1: The RP1 and IRP bits are reserved; always maintain these bits clear.

Data

Memory

Indirect AddressingDirect Addressing

Bank Select Location Select

RP1

(1)

RP0 6

From Opcode

IRP

(1)

FSR Register

Bank Select

Location Select

00 01 10 11

180h

1FFh

00h

7Fh

Bank 0 Bank 1 Bank 2 Bank 3

Not Used

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 127 128

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