creating delay

This is a discussion on creating delay within the C Programming forums, part of the General Programming Boards category; for(i=0; i<=15; i++){ //do nothing } How many processor cycles is this delay? Is there a more efficient way to ...

  1. #1
    Registered User
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    creating delay

    for(i=0; i<=15; i++){
    //do nothing
    }

    How many processor cycles is this delay?
    Is there a more efficient way to create a delay in my embedded system?

    2) I want a delay of 1000 ns. My processor runs at 12Mhz.
    How many steps sould i create in the for loop?

  2. #2
    cereal killer dP munky's Avatar
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    Nov 2002
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    im pretty sure there is a way

    #include <windows.h>
    sleep(/*number of ms*/);

    if that doesnt work try looking for it(the sleep thing) on msdn
    guns dont kill people, abortion clinics kill people.

  3. #3
    Just Lurking Dave_Sinkula's Avatar
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    Re: creating delay

    >How many processor cycles is this delay?
    It will depend on what i is. Take a look at the generated assembly. For example, this is what I get with an int i.
    Code:
    stmt level    source
    
       1          void main(void)
       2          {
       3   1          int i;
       4   1          for(i = 0; i < 16; ++i)
       5   1          {
       6   2          }
       7   1      }
    
                 ; FUNCTION main (BEGIN)
                                               ; SOURCE LINE # 1
                                               ; SOURCE LINE # 2
                                               ; SOURCE LINE # 4
    ;---- Variable 'i' assigned to Register 'R6/R7' ----
    0000 E4            CLR     A
    0001 FF            MOV     R7,A
    0002 FE            MOV     R6,A
    0003         ?C0001:
                                               ; SOURCE LINE # 5
                                               ; SOURCE LINE # 6
    0003 0F            INC     R7
    0004 BF0001        CJNE    R7,#00H,?C0005
    0007 0E            INC     R6
    0008         ?C0005:
    0008 EF            MOV     A,R7
    0009 6410          XRL     A,#010H
    000B 4E            ORL     A,R6
    000C 70F5          JNZ     ?C0001
                                               ; SOURCE LINE # 7
    000E         ?C0004:
    000E 22            RET     
                 ; FUNCTION main (END)
    Now comes the fun of looking up the instruction cycle times.

    >Is there a more efficient way to create a delay in my embedded system?
    Timer interrupts come to mind. You might find some useful information here.
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

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