[51] Generate a square wave with duty-cicle of 70% on 8051 (assembly)

[Junio Avelinor]

1)Hi. Good Morning, I'm having many doubts to generate a SQUARE wave with DUTY-CYCLE of N% on 8051.
1.1)I don't know but, to generate 50% is easy, but 66% or 78% is not.

2)The problems are in CALCULUS and The CODE in ASSEMBLY.
3)Some codes uses Interrupt, others not.


4) I also like to create a control like below, BUT I do not understand the principles.

duty cycle = Ton / Ton + Toff

duty cycle = 1s / 1s + 3s = 1s / 4s = 0.25



5) Are These informations enough to program the code ?

//ASSUME DUTY CYCLE 70%
//Crystal 12MHZ CLOCK.
//USE TIMERS
//CHECK OUT PUT IN P3.2




6) PLEASE COMMENT THE CODE

7) THANKS FOR YOUR HELP, GOD BLESS YOU

 

[paulfjujo]

hello,

before to adjust the duty ratio, you must define the Frequency of the square wave
Periode= 1/F
so you know Periode T = 100% of Duty
you define the time for 1% ( we can suppose that 1% of resolution is enough)
and apply the "regle de 3 " for every duty value do you want
use a timer to count elementary time for 1%

SQ freq=1Khz T=1mS =1000µs
adjust timer0 for 10µs interrupt
for Duty=68% ,
output =1 during 68 interrupts ..
after Output=0 during (100-68) interrupts

or use simple delay loops

or better solution : use PWM !
define the Frequency
adjust the Duty

 

[D.A.(Tony)Stewart]

70% AND SQUARE WAVE is an OXYMORON.
Anything not 50% is a rectangular pulse .

using positive logic 0% is low 100% is high.

the timer length reduces output frequency by n which is the total counts for Ton + Toff.
Choose any value of n such as 1024.