Discussion in "8051 Discussion Forum" started by    Dan51    Oct 25, 2007.
Thu Oct 25 2007, 11:49 AM
#1
Hello all

I have just started using the SDCC compiler for 8051.
I am trying to write an assembler function (Delay) inside a C file. It has to be written in assembler because the delay has to be accurate. I then want to call this function from a C function:


_asm
Delay:
mov r0, #FF
d100: djnz r0, d100
ret
_endasm


main()
{
_asm
call Delay
-endasm
}

The above code does not compile.
Is this possible to do some how?
Is there a better way to create an accurate delay function?

Thanks
Thu Oct 25 2007, 12:30 PM
#2
i guess it should be the other way

delay(){
_asm
mov r0, #FF
d100: djnz r0, d100
_endasm
}

and in main.. call delay as a function
Thu Oct 25 2007, 02:35 PM
#3
Thanks, this is correct, but then I am not sure I know how to calcuate the time (clocks) required for calling the delay function in C. This may cause a samll error in the delay time. Am I correct?
Thu Oct 25 2007, 03:11 PM
#4
not much.. after compiling its just a call to the function nothing much.
calling a function takes about 3 machine cycles, ret need 2 and rest is whats inside your loop
i have explained someone regarding how to calculate delay.. you can check that thread..
 Dan51 like this.
Thu Oct 25 2007, 04:51 PM
#5
OK, thanks a lot!

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ExperimenterUK
Sat Oct 12 2019, 10:23 PM
Log in.. then post your code in the 8051 forum
Sat Oct 12 2019, 10:18 AM
Bhadra Sajikumar
i am doing a countdown timer with 8051 for my project, unfortunately our professor had to take a leave of absence before he could teach us most of it.. can someone explain the .asm code of it for me?
Mon Sep 23 2019, 07:37 AM
Nathaniel
I am doing a project for my schools wireless security system with cameras,sensors and spot lights using 8051 micro controller, could you help me out with the design and its source code.
Wed Sep 18 2019, 08:48 PM
Caryn Kover
Thank you for your time,
ExperimenterUK
Mon Aug 05 2019, 07:09 PM
@Ismail ..post in forum, give details
Mon Aug 05 2019, 04:33 PM
Ismail balghmi
Hello. Please I won't download
ExperimenterUK
Wed Jul 24 2019, 12:47 AM
@BUSTER123 Please post in the forum
Tue Jul 23 2019, 06:13 PM
BUSTER123
hello! newbie here. i am kind of a guy who hates using ready - made existing libraries, so this helped a lot as i was trying to control and write to a character lcd display. however, i can't figure out how to set the cursor position. for example, i want to set it to the 5th column in the first row, so position 5. so according to the table, i am sending 10000101 on the 8 data lines of the lcd (register select pulled low). the cursor does not move there however. and i cant move the cursor left or right too. is it something wrong that i am doing? thank you.
ExperimenterUK
Thu Jul 11 2019, 07:55 PM
@ramos https://www.theengineeringprojects.com/2017/09/l298-motor-driver-library-proteus.html
ExperimenterUK
Thu Jul 11 2019, 07:44 PM
@praveen123. Can you give a link to the project ?

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