Datasheet

 1998-2013 Microchip Technology Inc. DS30605D-page 27
PIC16C63A/65B/73B/74B
4.5 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 reg-
ister. Any instruction using the INDF register actually
accesses the register pointed to by the File Select Reg-
ister, 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 4-4.
A simple program to clear RAM locations 20h-2Fh
using indirect addressing is shown in Example 4-2.
EXAMPLE 4-2: 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
FIGURE 4-4: DIRECT/INDIRECT ADDRESSING
Note: Maintain the IRP and RP1 bits clear.
Note 1: For register file map detail, see Figure 4-2.
2: Shaded portions are not implemented; maintain the IRP and RP1 bits clear.
Data
Memory
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
not used
FFh
80h
7Fh
00h
17Fh
100h
1FFh
180h
0
0