Datasheet

PIC16C62X
DS30235J-page 24  2003 Microchip Technology Inc.
4.4 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 4-9. However, IRP
is not used in the PIC16C62X.
A simple program to clear RAM location 20h-7Fh using
indirect addressing is shown in Example 4-1.
EXAMPLE 4-1: INDIRECT ADDRESSING
FIGURE 4-9: DIRECT/INDIRECT ADDRESSING PIC16C62X
movlw 0x20 ;initialize pointer
movwf FSR ;to RAM
NEXT clrf INDF ;clear INDF register
incf FSR ;inc pointer
btfss FSR,7 ;all done?
goto NEXT ;no clear next
;yes continue
CONTINUE:
For memory map detail see (Figure 4-4, Figure 4-5, Figure 4-6 and Figure 4-7).
Note 1: The RP1 and IRP bits are reserved; always maintain these bits clear.
Data
Memory
Indirect AddressingDirect Addressing
bank select location select
RP1 RP0
(1)
6
0
from opcode
IRP
(1)
FSR register
7
0
bank select
location select
00 01 10 11
180h
1FFh
00h
7Fh
Bank 0 Bank 1 Bank 2 Bank 3
not used