4 Replies Latest reply on Dec 4, 2014 4:20 PM by user_14586677

    Sticky bits

    srihari.s

       Hello ALL

         

      I was going through the SPI datasheet and near TX and RX status register part i found this word "Sticky bits"

         

      What are sticky bits

        • 1. Re: Sticky bits
          user_1377889

          Sticky bits keep their value when they changed to logical 1 as long until the status-register is read by the CPU. This is very important when the sticky bit is generating an interrupt, it has to be cleared within the isr. Otherwise the interrupt handling will not function properly.

             

           

             

          Bob

          • 2. Re: Sticky bits
            alex.lin

             Thanks, Bob. Clear and concise.

            • 3. Re: Sticky bits
              user_1377889

              Alex, welcome in the forum and in the fascinating world of PSoCs!

                 

              Nice to see that you found this two-year old post of mine ;-)

                 

              Can I help you with something more actual?

                 

               

                 

              Bob

              • 4. Re: Sticky bits
                user_14586677

                From the TRM

                   

                 

                   

                Sticky Status, with Clear on Read

                   


                In this mode, the status register inputs are sampled on each
                cycle of the status and control clock. If the signal is high in a
                given sample, it is captured in the status bit and remains
                high, regardless of the subsequent state of the input. When
                the CPU or DMA reads the status register the bit is cleared.
                The status register clearing is independent of mode and
                occurs even if the UDB clock is disabled; it is based on the
                bus clock and occurs as part of the read operation.

                   

                 

                   

                Regards, Dana.