
2002 Microchip Technology Inc.
DS30325B-page 27
PIC16F7X
2.5
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
A simple program to clear RAM locations 20h-2Fh
EXAMPLE 2-2:
INDIRECT ADDRESSING
FIGURE 2-5:
DIRECT/INDIRECT ADDRESSING
MOVLW
0x20
;initialize pointer
MOVWF
FSR
;to RAM
NEXT
CLRF
INDF
;clear INDF register
INCF
FSR,F
;inc pointer
BTFSS
FSR,4
;all done?
GOTO
NEXT
;no clear next
CONTINUE
:
;yes continue
Note
Data
Memory(1)
Indirect Addressing
Direct Addressing
Bank Select
Location Select
RP1:RP0
6
0
From Opcode
IRP
FSR Register
7
0
Bank Select
Location Select
00
01
10
11
Bank 0
Bank 1
Bank 2
Bank 3
FFh
80h
7Fh
00h
17Fh
100h
1FFh
180h