5 Replies Latest reply on Feb 1, 2017 10:06 PM by gsns

    Flash command sequence timeout?

    dennis.kelley

      I am planning on using the 29 series parts in a buss design sharing the buss with a SRAM part.  The question arose as to whether there is a timout on the command sequence to perform a write or erase command sequence.  For example I am writing the command sequence to do an erase, and my software needs to access the SRAM.  Both have their own CS so the Flash will not pay any attention to the buss activity for the SRAM access.  But can I be a few commands into the command sequence, and have a pause while the micro does the SRAM access, and then just pick up where I left off in the command sequence?

         

      Thanks,

         

      Dennis

        • 1. Re: Flash command sequence timeout?
          gsns

          Hi Dennis,

             

          Yes it is possible but you need to make sure that the chip select is low i.e the flash part is selected. But if you make chip select of the flash high while accessing SRAM then it will not work.

             

          Thanks,

             

          Krishna.

          • 2. Re: Flash command sequence timeout?
            dennis.kelley

            This is a separate SRAM part.  Just making sure you understand that?

               

            So if I deselect the Flash part while I r/w to the SRAM then I have to start the sequence over?

               

            That does not apply while waiting for an erase or write to flash though right?  I don't lock up bus for 2 seconds to erase the flash memory?

               

            Is any of this documented anywhere in a datasheet or app note?

               

            Thanks for the reply!

               

            Dennis

            • 3. Re: Flash command sequence timeout?
              gsns

              Hi Dennis,

                 

              Yes I understand that you are using a separate SRAM device.

                 

              Q) So if I deselect the Flash part while I r/w to the SRAM then I have to start the sequence over?

                 

              A. Yes. 

                 

              Q)That does not apply while waiting for an erase or write to flash though right?  I don't lock up bus for 2 seconds to erase the flash memory?

                 

              A. Yes it will not apply for an erase or write. You can not stop in the midst of an erase or write program. Once any operation starts you can introduce any delay and come back later to finish it.

                 

              Q) Is any of this documented anywhere in a datasheet or app note?

                 

              A. No it is not documented.

                 

              Thanks,

                 

              Krishna.

              • 4. Re: Flash command sequence timeout?
                dennis.kelley

                The data sheet clearly show CE/ going high between successive write during the program sequence?

                   

                My micro will also toggle CS/ and WE/ high and low during each successive write sequence?

                   

                This makes no sense?

                   

                 

                   

                • 5. Re: Flash command sequence timeout?
                  gsns

                  Hi Dennis,

                     

                  Sorry for the mistake in my previous response.

                     

                  The diagram in the datasheet is correct. You can de-select the Flash during command sequence, access to SRAM, and then continue the Flash command sequence. And you do not have to keep selecting the Flash while waiting for erase / program completion .

                     

                  For the SPI Flash, you must keep the CS# low during one command transfer.

                     

                  Hope it clears the confusion and clarifies your query. Let me know if you need any other clarifications.

                     

                  Please check the attached file

                     

                   

                     

                  Thanks,

                     

                  Krishna.