PIC16LC712-04SLASHSS datasheet(20/108 Pages) MICROCHIP

20 / 108 page

PIC16C712/716

DS41106A-page 20

Preliminary

2.5

Indirect Addressing, INDF and FSR

Registers

The INDF register is not a physical register. Address-

ing INDF actually addresses the register whose

address is contained in the FSR register (FSR is a

pointer). This is indirect addressing.

EXAMPLE 2-1:

INDIRECT ADDRESSING

• Register file 05 contains the value 10h

• Register file 06 contains the value 0Ah

• Load the value 05 into the FSR register

• A read of the INDF register will return the value of

10h

• Increment the value of the FSR register by one

(FSR = 06)

• A read of the INDR register now will return the

value of 0Ah.

Reading INDF itself indirectly (FSR = 0) will produce

00h. Writing to the INDF register indirectly results in a

no-operation (although STATUS bits may be affected).

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

using indirect addressing is shown in Example 2-2.

EXAMPLE 2-2:

HOW TO CLEAR RAM

USING INDIRECT

ADDRESSING

movlw

0x20

;initialize pointer

movwf

FSR

;

to RAM

clrf

INDF

;clear INDF register

incf

FSR

;inc pointer

btfss

FSR,4 ;all done?

goto

;NO, clear next

CONTINUE

;YES, continue

An effective 9-bit address is obtained by concatenating

the 8-bit FSR register and the IRP bit (STATUS<7>), as

shown in Figure 2-10. However, IRP is not used in the

PIC16C712/716.

FIGURE 2-10: DIRECT/INDIRECT ADDRESSING

Note 1: For register file map detail see Figure 2-3.

2: Maintain clear for upward compatibility with future products.

3: Not implemented.

Data

Memory(1)

Indirect Addressing

Direct Addressing

bank select

location select

RP1:RP0

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

(3)

(2)

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