How to make a delay in assembly for 8051 microcontrollers? -

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i having problem in calculating delays. want make delay 0.5 sec when using 1mhz clock speed 8051 microcontroller.

i use proteus simulation , avr studio coding in assembly atmel microcontroller.

for example code 8mhz clock microcontroller

delay_15ms: ldi dly1,  120  ;  delay1:     ldi  dly2, 250  ; delay2:     dec     dly2 ;      nop  ;      brne   delay2  ;       dec   dly1 ;     brne    delay1  ;  ret

can teach me how calculate time delay take? make 1 0.5 sec delay @ 1 mhz

thank you

0,5 s eternity in life of (even slow) microcontroller.

do realize not able while waiting ? ( called passive wait )

phil wetzel gave in comment link post describing interrupts. that's need.

it require read datasheet know how configure clocking system, how configure timer, how set , write interrupt timer...

however answer question ( if code snippet correct (?) ): 15 ms timeout on 8 mhz system realize 120 times second loop (delay2).

so have 8 times slower system want wait 0.5/0.015 = 33.33... times more.

so wait 120 / 8 * 0.5 / 0.015 = 500 delay1 loops

but µc 8 bit one, can not store such value in 8 bits register.

so fear asking impossible ( unless write code handle 16 bits variable ). may create delay0 loop , wait 2 times 250 delay1 loops.

not sure accuracy !!


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