How to properly do hardware delay

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Hi,

Anyone can help me to check the simple code (the program is work).

The problem is when i using Keil to simulate the result is.. 1.029805sec at 1000 looping but...when practically is not ~1sec (it take more then few min).

So, i change it to 1 at DELAY_T0_Wait(1); then in practical the result nearly to ~1sec.

The hardware crystal is 11.059MHz.

Can anyone tell me why?

Thank
 

Re: Hardware Delay

Hello

This is a wrong way to do hardware delay!

You should set the timer for periodic inerrupt who increase a long type variable

TimeValue = TimeValue +1;

when you wish to start a delay you need to save this register value + the delay

period.

Temp = TimeValue + Delay;

for testing create an if loop who read the variable and coper it to the one you saved once the value are equle or large then -> the delay is over

DlayFlag = 0;
Temp2 = TimeValue;
if(Temp >= Temp2)
DlayFlag = 1;


All the best

Bobi
 

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Re: Hardware Delay

Hi Friend,

Very happy you can explain to me but i still got a bit blur blur..., please can you help me to modified my code. So, i can study/try from the code, if i still not understand it so we come and discuss more further can we?

Thank You
 

Re: Hardware Delay

I can't see anything wrong with this code (from Chapter 6: "Meeting real-time constrains", Embedded C), even if it doesn't use interrupts ..
Can you post the compiled code which you try to use in real microcontroller ..
Regards,
IanP
 

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Re: Hardware Delay

hi,

I am using that i post it to run it in real microcontroller. Only the different with the code is.. the book is given DELAY_T0_Wait(1000); then i change it to DELAY_T0_Wait(1); because if i using the book given value i can't achieve ~1sec in real microcontroller.

Do you got any idea??

Thank You
 

Re: Hardware Delay

I checked the HEX file from your ZIP, disassembled it and couldn't find any errors ..

Then I tested your code in 87C52 micro and as it is I have 1.2ms square wave on pin 1.0, so I assume if N=1000 the square wave would have 1.2s ..

Regards,
IanP
 

Re: Hardware Delay

Hi,

So, you mean that is no problem with the code when you using my code? you got change the N=1000 or N=1 on code then run it in practical way? At N=1000 the code i need to wait the pin1.0 with LED blinking very long...what's the broblem?? Is it my hardware problem??

Thanks..
 

Re: Hardware Delay

That is correct, the software runs well ..

Just to make sure that it also performes with N=1000, can you compile new files with N=1000 and post them?

If you can, replace microcontroller with another 8051-compatibile, and check if the clock frequency is 11,059200 ..

Regards,
IanP
 

Re: Hardware Delay

Hi,

I already post N=1000 and N=1 Hex file to you, please try and see...

I only have 89c52 and i am using 11.059M crystal..

Thanks A Lot....
 

Re: Hardware Delay

I have tried the N=1000 option and the resultant square wave has ≈0.7s period ..
So, more than less it is manageable ..
On the other hand why your 89C52 behaves differently .. I really don't know ..
Regards,
IanP
 

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