Arduino_Assembly/Assembly_Blink_LED.S at main · jas2648/Arduino_Assembly · GitHub

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;------------------------
; Assembly Code
;------------------------
#define __SFR_OFFSET 0x00
#include "avr/io.h"
;------------------------
.global start
.global led
;------------------------
start:
    SBI   DDRB,4        ;set PB5 (D12) as o/p
    RET                 ;return to setup() function
;----------------------------------------------------------------------
led:
    CPI   R24, 0x00     ;value passed by caller in R24 compared with 0
    BREQ  ledOFF        ;jump (branch) if equal to subroutine ledOFF
    SBI   PORTB, 4      ;set D12 to high
    RET                 ;return to loop() function
;----------------------------------------------------------------------
ledOFF:
    CBI   PORTB, 4      ;set D12 to low
    RCALL myDelay
    RET                       ;return to loop() function
;---------------------------------------------------------------------------
.equ  delayVal, 10000         ;initial count value for inner loop
;---------------------------------------------------------------------------
myDelay:
    LDI   R20, 100            ;initial count value for outer loop
outerLoop:
    LDI   R30, lo8(delayVal)  ;low byte of delayVal in R30
    LDI   R31, hi8(delayVal)  ;high byte of delayVal in R31
innerLoop:
    SBIW  R30, 1              ;subtract 1 from 16-bit value in R31, R30
    BRNE  innerLoop           ;jump if countVal not equal to 0
    ;--------------
    SUBI  R20, 1              ;subtract 1 from R20
    BRNE  outerLoop           ;jump if R20 not equal to 0
    RET
;---------------------------------------------------------------------------