PIC12F629/675
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
MOVWF
CLRF
INCF
BTFSS
GOTO
0x20
FSR
INDF
FSR
;initialize pointer
;to RAM
;clear INDF register
;inc pointer
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
(STATUS<7>), as shown in Figure 2-2.
NEXT
FSR,4 ;all done?
NEXT ;no clear next
;yes continue
CONTINUE
FIGURE 2-2:
DIRECT/INDIRECT ADDRESSING PIC12F629/675
Direct Addressing
From Opcode
Indirect Addressing
(1)
(1)
7
RP1
RP0
6
0
0
IRP
FSR Register
Bank Select
180h
Location Select
Bank Select Location Select
00
01
10
11
00h
Data
Not Used
Memory
7Fh
1FFh
Bank 0
Bank 1
Bank 2
Bank 3
For memory map detail see Figure 2-2.
Note 1: The RP1 and IRP bits are reserved; always maintain these bits clear.
DS41190G-page 20
2010 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
