PIC10F220IP(2006) 查看數據表（PDF） - Microchip Technology
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PIC10F220IP Datasheet PDF : 78 Pages
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PIC10F220/222
4.9 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.
4.9.1 INDIRECT ADDRESSING
• Register file 09 contains the value 10h
• Register file 0A contains the value 0Ah
• Load the value 09 into the FSR register
• A read of the INDF register will return the value
of 10h
• Increment the value of the FSR register by one
(FSR = 0A)
• A read of the INDR register now will return the
value of 0Ah.
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).
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
The FSR is a 5-bit wide register. It is used in conjunc-
tion 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.
Note: Do not use banking. FSR <7:5> are
unimplemented and read as ‘1’s.
FIGURE 4-6:
DIRECT/INDIRECT ADDRESSING
Direct Addressing
Indirect Addressing
4 (opcode) 0
4 (FSR) 0
Location Select
00h
Location Select
Data
0Fh
Memory(1) 10h
1Fh
Bank 0
Note 1: For register map detail, see Section 4.3 “Data Memory Organization”.
DS41270B-page 20
Preliminary
© 2006 Microchip Technology Inc.
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