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Russ Cooper
01/04/08 11:04
Read: 1075 times
Phoenix, Az

#149055 - Variable delay
Responding to: Jan Waclawek's previous message
The place where I used that routine was indeed one of those 1% of the 1% of the 1% cases that you don't run into very often.

A pal and I were building a tester that needed to put out a couple of pulses with a certain delay between them, where the delay had to be adjustable over a certain range with as fine a resolution as we could come up with. We wound up using a 100 MHz SiLabs screamer, which gave us 10 ns resolution on the delay. 5 ns resolution would have been better, but we got by.

I can't honestly say I ever thought about the caching issues, but I can say that the results we got were predictable and stable. Maybe reason was that the testing loop was so small and simple that the cache behaved the same way every time. Probably?

-- Russ

List of 27 messages in thread
Number of CPU cycle for 8051 function call      Jae-yong Kim      01/04/08 01:03      
   Do it in assembler      Andy Neil      01/04/08 03:00      
   Delay functions      Andy Neil      01/04/08 03:07      
   A related trick        Russ Cooper      01/04/08 05:56      
      Offset      Andy Neil      01/04/08 07:03      
         Offset      Russ Cooper      01/04/08 07:23      
            Sure      Andy Neil      01/04/08 07:40      
               Over Drive?      Neil Kurzman      01/04/08 10:20      
      a refinement      Erik Malund      01/04/08 07:58      
      NOPs are so bad waste of space...      Jan Waclawek      01/04/08 08:51      
         waste of space... waste of time      Erik Malund      01/04/08 09:24      
            fixed delay      Jan Waclawek      01/04/08 09:54      
               Variable delay      Russ Cooper      01/04/08 11:04      
                  determinism of the cache      Jan Waclawek      01/04/08 11:36      
               there are no cache misses in 'linear code'      Erik Malund      01/04/08 11:16      
                  I got only ONE cache miss...      Jan Waclawek      01/04/08 11:39      
      Old Keil Thread      Jon Ward      01/06/08 18:29      
   What about a Delay like this.      Jerry Black      01/07/08 05:31      
      No, it won't.        Christoph Franck      01/07/08 05:55      
         Ok.      Jerry Black      01/07/08 07:08      
         also      Erik Malund      01/08/08 06:47      
      Also ...      Christoph Franck      01/08/08 07:01      
         Actually...      Brett Wallace      01/08/08 08:02      
            will.      Jerry Black      01/08/08 08:21      
               ANSI C      Maarten Brock      01/10/08 05:58      
                  Keil option: Disable ANSI casts      Andy Neil      01/10/08 07:08      
         typo.      Jerry Black      01/08/08 08:24      

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