Datasheet

PIC14000

DS40122B-page 24 Preliminary  1996 Microchip Technology Inc.

4.4 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

actually accesses data pointed to by the ﬁle select

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 4-10. However, IRP

is not used in the PIC14000.

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

indirect addressing is shown in Example 4-2.

EXAMPLE 4-2: INDIRECT ADDRESSING

movlw 0x20 ;initialize pointer

movf FSR ;to RAM

NEXT clrf INDF ;clear INDF register

incf FSR ;inc pointer

btfss FSR,4 ;all done?

goto NEXT ;no clear next

;yes continue

CONTINUE:

FIGURE 4-10: INDIRECT/INDIRECT ADDRESSING

Note: For memory map detail see Figure 4-1.

01 10 11

IRP 7 FSR 00

bank select

location select

from opcode

location select

bank select

RP1

RP0

Indirect Addressing

Direct Addressing

Data

Memory

not used

Bank 0

Bank 1 Bank 2 Bank 3