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;**** A P P L I C A T I O N N O T E A V R 1 0 8 ************************ ;* ;* Title: Load Program Memory ;* Version: 1.0 ;* Last updated: 98.02.27 ;* Target: AT90Sxx1x and higher (Devices with SRAM) ;* ;* Support E-mail: avr@atmel.com ;* ;* DESCRIPTION ;* This Application note shows how to use the Load Program Memory (LPM) ;* instruction. The App. note loads the string "Hello World" from ;* program memory byte by byte, and puts it onto port B. ;* ;*************************************************************************** .include "8515def.inc" .device AT90S8515 ; Specify device .def temp =r16 ; Define temporary variable start: ldi temp,low(RAMEND) out SPL,temp ; Set stack pointer to last internal RAM location ldi temp,high(RAMEND) out SPH,temp ldi temp,$ff out PORTB,temp ; Set all pins at port B high out DDRB,temp ; Set port B as output ; Load the address of 'message' into the Z register. Multiplies ; word address with 2 to achieve the byte address, and uses the ; functions high() and low() to calculate high and low address byte. ldi ZH,high(2*message); Load high part of byte address into ZH ldi ZL,low(2*message); Load low part of byte address into ZL loadbyte: lpm ; Load byte from program memory into r0 tst r0 ; Check if we've reached the end of the message breq quit ; If so, quit out PORTB,r0 ; Put the character onto Port B rcall one_sec_delay ; A short delay adiw ZL,1 ; Increase Z registers rjmp loadbyte quit: rjmp quit one_sec_delay: ldi r20, 20 ldi r21, 255 ldi r22, 255 delay: dec r22 brne delay dec r21 brne delay dec r20 brne delay ret message: .db "Hello World" .db 0 |