PIC16F688
A simple program to clear RAM location 20h-2Fh using
indirect addressing is shown in Example 2-1.
2.4
Indirect Addressing, INDF and
FSR Registers
The INDF register is not a physical register. Addressing
the INDF register will cause indirect addressing.
EXAMPLE 2-1:
INDIRECT ADDRESSING
MOVLW 0x20
MOVWF FSR
;initialize pointer
;to RAM
;clear INDF register
;inc pointer
;all done?
;no clear next
;yes continue
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 2-4.
NEXT CLRF
INCF
INDF
FSR
BTFSS FSR,4
GOTO
NEXT
CONTINUE
FIGURE 2-4:
DIRECT/INDIRECT ADDRESSING PIC16F688
Direct Addressing
Indirect Addressing
From Opcode
7
RP1
RP0
6
0
0
IRP
File Select Register
Bank Select
180h
Location Select
Bank Select
Location Select
00h
00
01
10
11
Data
Memory
7Fh
1FFh
Bank 0
Bank 1
Bank 2
Bank 3
Note:
For memory map detail, see Figure 2-2.
DS41203D-page 20
© 2007 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
