Conference 49.910::kav30

127.0. "Timer value used in kav$timers" by ZYDECO::REDDY () Fri May 27 1994 02:29

Hello,



In the KAV30 manual, it gives the following for timer count, if one wants the 
timer to expire every second:

	    timer_count = (65536 * (1000 - 1)) + 2500

    kav$timers (NULL, 			/* Return Status */
      timer_functions, 			/* Timer functions to perofrm */
      KAV$K_CTMR0, 			/* Timer number to use */
      &timer_count, 			/* value to load into timer register */
      NULL, 				/* AST address */
      NULL);				/* AST parameter */


One of cur customers used the following calculation so that the timer would
expire every 1/10 of a second:

                timer_count = (65536 * (100 - 1)) + 2500

When using this calculation they found their timing to be off about 3 seconds 
every 5 minutes.  They discovered that removing the "- 1" from the above 
algorithm corrected the timing problem.  They want to know if this is a 
documentation problem, or something they are doing?

Based on the documentation, if they remove "-1", aren't they waiting for a 
little more than a 1/10 of a second?

Any ideas on why they might be losing time using the timer isrs would be 
appreciated.

Thanks,

Sumithra
                                                                                
    

    I would guess a documentation problem, but I check it anyways
    
    	Julian.
    

    
    Thanks
    

    The documentation is wrong. It should have been corrected in the ELN
    V4.4 docset, but it is obviously not....
    
    	Julian.
    

    
    Julian,
    
    When you say that the documentation is wrong, does it mean that if I
    wanted the timer to expire after one second, I would have the following
    for the timer_count?  
    
    	timer_count = (65536 * 1000) + 2500
    
    
    Thanks,
    
    Sumithra
    

    Sumithra,
    
    the answer is yes - the formula we supplied to the technical writer is:
    
    	timer_count = (65536 * ((1000 - 1)+1) + 2500
    
    but somehow the +1 got lost (probably it was too difficult to
    understand....)
    
    Thomas (for Julian)
    

    
    Thomas and Julian,
    
    Thanks.  I will let the customer know that te correct formula is
    timer_count = (65536 * ((1000 - 1)+1) + 2500.
    
    
    Sumithra