PIC16F7X Datasheet, PDF (29/174 Pages) Microchip Technology – 28/40-Pin 8-Bit CMOS FLASH Microcontrollers

PIC16F7X
2.5 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 2-5.
A simple program to clear RAM locations 20h-2Fh
using indirect addressing is shown in Example 2-2.
EXAMPLE 2-2: INDIRECT ADDRESSING
MOVLW
MOVWF
NEXT CLRF
INCF
BTFSS
GOTO
CONTINUE
:
0x20
FSR
INDF
FSR,F
FSR,4
NEXT
;initialize pointer
;to RAM
;clear INDF register
;inc pointer
;all done?
;no clear next
;yes continue
FIGURE 2-5:
DIRECT/INDIRECT ADDRESSING
Direct Addressing
RP1:RP0 6
From Opcode ₀
Indirect Addressing
IRP
7
FSR Register
0
Bank Select Location Select
00
00h
01
80h
10
100h
11
180h
Bank Select
Location Select
Data
Memory⁽¹⁾
7Fh
FFh
17Fh
1FFh
Bank 0 Bank 1 Bank 2 Bank 3
Note 1: For register file map detail, see Figure 2-2.
 2002 Microchip Technology Inc.
DS30325B-page 27