PIC16F688 Datasheet, PDF (22/174 Pages) Microchip Technology – 14-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F688
2.4 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
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 2-4.
A simple program to clear RAM location 20h-2Fh using
indirect addressing is shown in Example 2-1.
EXAMPLE 2-1: INDIRECT ADDRESSING
MOVLW
MOVWF
NEXT CLRF
INCF
BTFSS
GOTO
CONTINUE
0x20
FSR
INDF
FSR
FSR,4
NEXT
;initialize pointer
;to RAM
;clear INDF register
;inc pointer
;all done?
;no clear next
;yes continue
FIGURE 2-4:
DIRECT/INDIRECT ADDRESSING PIC16F688
Direct Addressing
RP1 RP0 6
From Opcode
0
Indirect Addressing
IRP
7
File Select Register 0
Bank Select
Location Select
00
01
00h
Bank Select
10
11
180h
Location Select
Data
Memory
Note:
7Fh
Bank 0
Bank 1
For memory map detail, see Figure 2-2.
Bank 2
Bank 3
1FFh
DS41203B-page 20
Preliminary
 2004 Microchip Technology Inc.