How to delay assembly for avr microcontrollers?

Question

I am having a problem calculating delays. I want to delay for 1 secwhen I use the clock frequency 1MHzfor my atmega128 microcontroller.

I use protus for modeling and avr studio for coding in assembly for the atmel microcontroller.

For example, this code is for 8MHza clock microcontroller

Delay_15mS:                 ; For CLK(CPU) = 8 MHz
    LDI     dly1,   120     ; One clock cycle;
Delay1:
    LDI     dly2,   250     ; One clock cycle
Delay2:
    DEC     dly2            ; One clock cycle
    NOP                     ; One clock cycle
    BRNE    Delay2          ; Two clock cycles for true 1 clock for false

    DEC     dly1            ; One clock Cycle
    BRNE    Delay1          ; Two clock cycles for true 1 clock for false
RET

Can you teach me how to calculate the time this delay will take? So I could do 1 on 1 s delay @ 1 MHz

thank

Answer 1

, , , .

1MHz clock 1000000 . , 1 1/1000000 1us. 1 , 1000000 1us, , 1000000.

, 1 sec delay @ 1MHz:

Delay_1sec:                 ; For CLK(CPU) = 1 MHz
    LDI     dly1,   8       ; 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

Delay3, 4 , DEC=1, NOP=1 BRNE=2 Delay3. , 4 250 ( dly3) - 1000 1000us= 1ms.

Delay2 Delay3 125 ( dly2). , 125ms.

, , Delay1 Delay2 8 ( dly1). , 1000ms 1 second.

. , 1sec, Delay2 Delay1. , 1sec , dly1, dly2 dly3 , , t21 .

2. , . , timers .

Answer 2

/. /0 prescalar=1024 1MHz 250ms. 250 . 4 1 second!