Datasheet

PIC16F7X7
DS30498D-page 30  2003-2013 Microchip Technology Inc.
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 the register pointed to by the File
Select Register, 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 (Status<7>) as shown in Figure 2-5.
A simple program to clear RAM locations 20h-2Fh
using indirect addressing is shown in Example 2-2.
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 1: For register file map detail, see Figure 2-2.
Data
Memory
(1)
Indirect AddressingDirect 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