PIC16F526 Datasheet, PDF (22/122 Pages) Microchip Technology – 14-Pin, 8-Bit Flash Microcontroller

PIC16F526
4.8 Indirect Data Addressing: INDF
and FSR Registers
The INDF Register is not a physical register.
Addressing INDF actually addresses the register
whose address is contained in the FSR Register (FSR
is a pointer). This is indirect addressing.
Reading INDF itself indirectly (FSR = 0) will produce
00h. Writing to the INDF Register indirectly results in a
no-operation (although Status bits may be affected).
The FSR is an 8-bit wide register. It is used in
conjunction with the INDF Register to indirectly
address the data memory area.
The FSR<4:0> bits are used to select data memory
addresses 00h to 1Fh.
FSR<6:5> are the bank select bits and are used to
select the bank to be addressed (00 = Bank 0,
01 = Bank 1, 10 = Bank 2, 11 = Bank 3).
FSR<7> is unimplemented and read as ‘1’.
A simple program to clear RAM locations 10h-1Fh
using indirect addressing is shown in Example 4-1.
EXAMPLE 4-1:
HOW TO CLEAR RAM
USING INDIRECT
ADDRESSING
NEXT
MOVLW
MOVWF
CLRF
INCF
BTFSC
GOTO
CONTINUE
:
:
0x10
FSR
INDF
FSR,F
FSR,4
NEXT
;initialize pointer
;to RAM
;clear INDF
;register
;inc pointer
;all done?
;NO, clear next
;YES, continue
FIGURE 4-4:
DIRECT/INDIRECT ADDRESSING
Direct Addressing
(FSR)
(opcode)
65
43 2 10
Indirect Addressing
(FSR)
6 543 2 1 0
bank select location select
00
01
10
11
00h
bank
select
location select
Data
0Ch
Memory⁽¹⁾ _0Dh
0Fh
10h
Addresses map back to
addresses in Bank 0.
2Fh
4Fh
6Fh
1Fh
3Fh
5Fh
7Fh
Bank 0 Bank 1 Bank 2 Bank 3
Note 1: For register map detail see Figure 4-1.
DS41326D-page 22
 2010 Microchip Technology Inc.