PIC16C620 Microchip Technology, PIC16C620 Datasheet - Page 24

• Manufacturer Part Number: PIC16C620
• Description: EPROM-Based 8-Bit CMOS Microcontroller
• Manufacturer: Microchip Technology

PIC16C62X
4.4
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 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 4-15. However, IRP is not used in the
PIC16C62X.
A simple program to clear RAM location 20h-2Fh using
indirect addressing is shown in Example 4-1.
FIGURE 4-15: DIRECT/INDIRECT ADDRESSING PIC16C62X
DS30235G-page 24
(1)
bank select
RP1 RP0
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.
Indirect Addressing, INDF and FSR
Registers
location select
6
Direct Addressing
Data
Memory
from opcode
7Fh
00h
Bank 0
00
0
Bank 1
01
Preliminary
Bank 2
10
not used
NEXT
CONTINUE:
EXAMPLE 4-1:
Bank 3
11
IRP
movlw
movwf
clrf
incf
btfss
goto
bank select
180h
1FFh
(1)
INDIRECT ADDRESSING
0x20
FSR
INDF
FSR
FSR,4
NEXT
7
Indirect Addressing
1998 Microchip Technology Inc.
;initialize pointer
;to RAM
;clear INDF register
;inc pointer
;all done?
;no clear next
;yes continue
FSR register
location select
0