1 Reply Latest reply on Jan 28, 2016 11:17 AM by scott.carlson

    sram won't read msb of address

    scott.carlson

      I switched srams, to a 16 bit sram with 18 address bits and now I cannot read/write to the external sram when I'm accessing anything using the msb (addr bits 16 and 17).  

         

       

         

      I found when I disconnect the 16 and 17 addr bits and tie them either high or low it works fine, but when its connected to the psoc and being selected by the emif component it displays the same thing on the lcd (i get changing values when its accessing only the lower 0-15 addrs bits or if 16 and 17 are not connected).

         

       

         

      this is consistent across gpio pins.  

         

       

         

      I'm using 512kbx16 sram: CY7C1041D 

         

       

         

      Its almost as if the way the psoc is interacting with the sram is messing it up somehow.

         

       

         

      Does anyone know what is going on?

        • 1. Re: sram won't read msb of address
          scott.carlson

          So the problem still persists.. although I thought I'd clarify some things

             

           

             

          The sram is async.

             

           

             

          the transfers to the ext sram are done via dma, while the reads are done directly using a pointer to the memory.  

             

           

             

          again this works for all addresses on the sram that doesn't address using the upper 2 msb's.  

             

           

             

          I have also verified the signals coming out of the psoc for address bits 16 and 17, and they seem to behave just as any of the other address bits are behaving.  If I disconnect both the 16 and 17 wires, and then plug them in individually, whatever port on the psoc that was addressing the 16th or 17th bit freezes the data on my lcd.