PIC16C65B Microchip Technology Inc., PIC16C65B Datasheet - Page 27

• Manufacturer Part Number: PIC16C65B
• Description: 8-bit Cmos Microcontrollers With A/d Converter
• Manufacturer: Microchip Technology Inc.

4.5
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.
FIGURE 4-4:
Note 1: For register file map detail, see Figure 4-2.
2000 Microchip Technology Inc.
RP1:RP0
bank select
0
2: Shaded portions are not implemented; maintain the IRP and RP1 bits clear.
Indirect Addressing, INDF and
FSR Registers
location select
6
Direct Addressing
Data
Memory
DIRECT/INDIRECT ADDRESSING
from opcode
00h
7Fh
Bank 0
00
0
80h
FFh
Bank 1
01
PIC16C63A/65B/73B/74B
100h
17Fh
Bank 2
10
not used
EXAMPLE 4-2:
NEXT
CONTINUE
Note:
180h
1FFh
Bank 3
11
Maintain the IRP and RP1 bits clear.
IRP
movlw
movwf
clrf
incf
btfss
goto
:
0
bank select
7
0x20
FSR
INDF
FSR,F
FSR,4
NEXT
Indirect Addressing
INDIRECT ADDRESSING
;initialize pointer
;to RAM
;clear INDF register
;inc pointer
;all done?
;no clear next
;yes continue
FSR register
DS30605C-page 27
location select
0