10F202 datasheet(19/88 Pages) MICROCHIP

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DS40001239F-page 19

PIC10F200/202/204/206

4.9

Indirect Data Addressing: INDF

and FSR Registers

The INDF register is not a physical register. Addressing

INDF actually addresses the register whose address is

contained in the FSR register (FSR is a pointer). This is

indirect addressing.

4.10

Indirect Addressing

• Register file 09 contains the value 10h

• Register file 0A contains the value 0Ah

• Load the value 09 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 = 0A)

• 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 10h-1Fh

using indirect addressing is shown in Example 4-1.

EXAMPLE 4-1:

HOW TO CLEAR RAM

USING INDIRECT

ADDRESSING

The FSR is a 5-bit wide register. It is used in

conjunction with the INDF register to indirectly address

the data memory area.

The FSR<4:0> bits are used to select data memory

addresses 00h to 1Fh.

FIGURE 4-6:

DIRECT/INDIRECT ADDRESSING (PIC10F200/202/204/206)

Note:

PIC10F200/202/204/206 – Do not use

banking. FSR <7:5> are unimplemented

and read as ‘1’s.

MOVLW

0x10

;initialize pointer

MOVWF

FSR

;to RAM

CLRF

INDF

;clear INDF

;register

INCF

FSR,F

;inc pointer

BTFSC

FSR,4

;all done?

GOTO

;NO, clear next

CONTINUE

;YES, continue

Note 1:

For register map detail, see Section 4.3 “Data Memory Organization”.

Location Select

Indirect Addressing

Direct Addressing

Data

Memory(1)

0Fh

10h

Bank 0

(FSR)

00h

1Fh

(opcode)

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