2 Replies Latest reply on Sep 6, 2014 4:36 AM by user_14586677

    Strange timing on pin writes

    user_362267832

       I'm seeing some strange behaviour writing to pins on a PSoC 5LP.  I'm writing a 6-bit value to six pins grouped as a bus.  I'm then writing a 1 followed by a 0 to a separate pin.  The changes on some of the bits within the bus don't always happen concurrently.  In fact, some of them occur *after* the strobe is cycled.

         

      Here's the code I'm using:

         

      P_Write(data);
      CyDelayUs(1);
      STB_Write(1);
      STB_Write(0);

         

      Here's what the resulting timing looks like.  Anyone know what's going on?

         
              
         
              
         
              
        • 1. Re: Strange timing on pin writes
          user_1377889

          It is a bit difficult to judge from a picture what the cause of the strange behavior is. Can you post your complete project, so that we all can have a look at all of your settings? To do so, use
          Creator->File->Create Workspace Bundle (minimal)
          and attach the resulting file (do NOT use chrome, that still may not work).

             

           

             

          Bob
           

          • 2. Re: Strange timing on pin writes
            user_14586677

            First the Saleae logic analyzer way too slow to get accurate timing.

               

            Although display you show is relatively (within 135 nS) correct.

               

             

               

            Consider a scope and look at the trigger vs a specific channel. In fact

               

            you can trigger DSO on a pin changing before strobe as a condition.

               

            Or on a condition of excessive delay of a pins response.

               

             

               

            What is used as the trigger, the STB ?

               

             

               

            Regards, Dana.