AVRアセンブラのテスト

http://necrobious.blogspot.jp/2010/06/avr-asm-first-steps.html
Arduino(ATmega328p)で約１秒周期でBlinkする
16MHzなので、16M cycle（16メガサイクル）回せば1秒ディレイする。
Cで書くときとの違いはスタックポインタの初期化が必要になるところ。(SRAM最後尾への配置を明示)

.include "m328def.inc" 

.def temp       = r16
.equ led        = 5                   ; PORTD bit number to blink LED on

.def dly1 = r17
.def dly2 = r18
.def dly3 = r19

.org 0x0000                             ; the next instruction will be written to 0x0000
rjmp main                               ; jump to main:

main:
        ldi     temp, low(RAMEND)       ; initiate the stack in the build in SRAM. Stack operations 
        out     SPL, temp               ; are always necessary when subroutines or interrupts are called.
        ldi     temp, high(RAMEND)      ; By calling the subroutine or interrupt handling routine the actual adress 
        out     SPH, temp               ; is written to the stack in order to later jump back to the code where the 
                                        ; interrupt or call occurred.

        sbi     DDRB, led               ; connect PORTD pin 4 to LED

loop:
        cbi     PORTB, led              ; turn PD4 high
        rcall   Delay_1sec                   ; delay for an short bit
        sbi     PORTB, led              ; turn PD4 low 
        rcall   Delay_1sec                   ; delay again for a short bit
        rjmp    loop                    ; recurse back to the start of loop:
Delay_1sec:                 ; For CLK(CPU) = 16 MHz  ; 4cycle * 250 * 125 * (8*16) = 16,000,000(16メガサイクル)
    LDI     dly1,   8*16       ; One clock cycle;
Delay1:
    LDI     dly2,   125     ; One clock cycle
Delay2:
    LDI     dly3,   250     ; One clock cycle
Delay3:
    DEC     dly3            ; One clock cycle
    NOP                     ; One clock cycle
    BRNE    Delay3          ; Two clock cycles when jumping to Delay3, 1 clock when continuing to DEC

    DEC     dly2            ; One clock cycle
    BRNE    Delay2          ; Two clock cycles when jumping to Delay2, 1 clock when continuing to DEC

    DEC     dly1            ; One clock Cycle
    BRNE    Delay1          ; Two clock cycles when jumping to Delay1, 1 clock when continuing to RET
RET

書き直し

.include "m328def.inc"
.org 0x0000
rjmp reset
reset:
    ldi R16,low(RAMEND)
    out SPL, R16
    ldi R16,high(RAMEND)
    out SPH, R16
main:
    sbi DDRB, 5
loop:
	sbi PORTB,5
        rcall delay
	cbi PORTB,5
	rcall delay
	rjmp loop
delay:
    ldi R17,16*4
delay1s:	
    ldi R18,250
delay250ms:
	ldi R19,250
delay1ms:
	nop
	dec R19
	brne delay1ms

	dec R18
	brne delay250ms

	dec R17
	brne delay1s
	ret