Datasheet

© 2009 Microchip Technology Inc. DS41341E-page 31
PIC16F72X/PIC16LF72X
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
register. Any instruction using the INDF register
actually 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 of
the STATUS register, as shown in Figure 2-8.
A simple program to clear RAM location 020h-02Fh
using indirect addressing is shown in Example 2-2.
EXAMPLE 2-2: INDIRECT ADDRESSING
FIGURE 2-8: DIRECT/INDIRECT ADDRESSING
MOVLW 020h ;initialize pointer
MOVWF FSR ;to RAM
BANKISEL 020h
NEXT CLRF INDF ;clear INDF register
INCF FSR ;inc pointer
BTFSS FSR,4 ;all done?
GOTO NEXT ;no clear next
CONTINUE ;yes continue
Note: For memory map detail, refer to Figures 2-4 and 2-5.
Data
Memory
Indirect AddressingDirect Addressing
Bank Select Location Select
RP1 RP0 6
0
From Opcode
IRP File Select Register
7
0
Bank Select
Location Select
00 01 10 11
180h
1FFh
00h
7Fh
Bank 0 Bank 1 Bank 2 Bank 3