PIC16LC8X-04 查看數據表（PDF） - Microchip Technology

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PIC16LC8X-04

8-Bit CMOS EEPROM Microcontrollers

Microchip Technology 

4.4 Indirect Addressing, INDF and FSR

Registers

The INDF register is not a physical register and is used

in conjunction with the FSR register to perform indirect

addressing.

Indirect addressing is possible by using the INDF

register. Any instruction using the INDF register

actually accesses data pointed to by the file select

register (FSR). 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). An effective 9-bit address is obtained by

concatenating the 8-bit FSR register and the IRP bit

(STATUS<7>), as shown in Figure 4-7. However, IRP

is not used in the PIC16C8X.

A simple program to clear RAM locations 20h-2Fh

using indirect addressing is shown in Example 4-1.

PIC16C8X

EXAMPLE 4-1: INDIRECT ADDRESSING

NEXT

CONTINUE

movlw

movwf

clrf

incf

btfss

goto

:

0x20 ;initialize pointer

FSR ; to RAM

INDF ;clear INDF register

FSR ;inc pointer

FSR,4 ;all done?

NEXT ;NO, clear next

;YES, continue

FIGURE 4-7: DIRECT/INDIRECT ADDRESSING

RP1 RP0

Direct Addressing

6 from opcode

0

Indirect Addressing

IRP

7

(FSR)

0

bank select location select

bank select

00

01

10

11

00h

00h

0Bh

not used

0Ch

2Fh (1)

30h (1)

mapped in

bank 0

4Fh (2)

50h (2)

7Fh

7Fh

Bank 0 Bank 1 Bank 2 Bank 3

Note 1: PIC16C83, PIC16CR83, and PIC16C84 devices.

2: PIC16C84A and PIC16CR84 devices

3: For memory map detail see Figure 4-1.

location select

© 1995 Microchip Technology Inc.

DS30081F-page 19

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