PIC16F1827 datasheet(21/406 Pages) MICROCHIP

Part #	PIC16F1827

Description	18/20/28-Pin Flash Microcontrollers with nanoWatt XLP Technology

PDF	406 Pages

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Manufacturer	MICROCHIP [Microchip Technology]

Direct Link	http://www.microchip.com

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 2010 Microchip Technology Inc.

Preliminary

DS41391C-page 21

PIC16F/LF1826/27

3.1.1

READING PROGRAM MEMORY AS

DATA

There are two methods of accessing constants in pro-

gram memory. The first method is to use tables of

RETLW instructions. The second method is to set an

FSR to point to the program memory.

3.1.1.1

RETLW Instruction

The RETLW instruction can be used to provide access

to tables of constants. The recommended way to create

such a table is shown in Example 3-1.

EXAMPLE 3-1:

RETLW INSTRUCTION

The BRW instruction makes this type of table very sim-

ple to implement. If your code must remain portable

with previous generations of microcontrollers, then the

BRW instruction is not available so the older table read

method must be used.

constants

brw

;Add Index in W to

;program counter to

;select data

retlw DATA0

;Index0 data

retlw DATA1

;Index1 data

retlw DATA2

retlw DATA3

my_function

;… LOTS OF CODE…

movlw

DATA_INDEX

call constants

;… THE CONSTANT IS IN W

PIC16F1827 Datasheet(PDF) 21 Page - Microchip Technology