7 Replies Latest reply on Nov 4, 2014 10:47 AM by agxinmj

    Getting two different results at same frequency .interactive vs DDRx Batch Mode

    sandeep.kumar

      Hi,

       

      I have simulated DDR address signals using Batch Mode then at 800 MHz the signal looks like ok,but when i

      simulated individually say DATA_5 line at 800 MHz then it gets distorted but at the same time when i change the

      frequency to 133 then the results are same as batch mode.

       

      My DDR data rate is 1600 MT/s so clock will be 800MHz.

      In Batch mode simulation is ok but individually it is distorted why ?

       

      Kindly reply.

        • 1. Re: Getting two different results at same frequency .interactive vs DDRx Batch Mode
          cristian.filip

          Check your settings (driver strength, terminations, corner case, probing location, etc.).

          • 2. Re: Getting two different results at same frequency .interactive vs DDRx Batch Mode
            sandeep.kumar

            Hi Cristian,

             

            I checked but the same result i got.

            My DDR is having data transfer speed of 1600 MT/S.

             

            In Hyperlynx Digital Oscilloscope window in oscillator section

            i have to take frequency 800 MHz. Am i correct?

             

            When i have taken 800MHz &  Interactively simulated then i have got

            a different result as compared to the batch mode.

             

            At 800 MHz thnal looks somewhat distorted but at 133MHz in digital oscilloscope

            window it looks fine.

             

            I am mailing you the simulation results as attachment is not allowed to be sent.

             

            1)I want to know why there is difference between interactive & Batch simulation at same

            frequency?

             

            2)I am taking 800MHz in digital oscilloscope window as my DDR is having data transfer rate of 1600MT/s

            is this frequency what i am feeding in oscilloscope is correct ?

             

             

            Thanks

            • 3. Re: Getting two different results at same frequency .interactive vs DDRx Batch Mode
              sandeep.kumar

              Please also clear one more thing :

               

              For DDR3 1600MT/s i.e. Clock = 800 MHz

               

              At 1T timing what will be the frequency of simulation for

               

              1) Address/Command signal

              2) Data signal

              3) Control Signal

               

              &

               

              for 2T timings what will be the frequecy of simulation for

               

              1) Address/Command signal

              2) Data signal

              3) Control Signal

               

               

              whether in Batch mode the tool itself adjusts frequency for ADDRESS/DATA/CONTROL signal once at initialization stage we feed the speed of DDR ?ds

               

              please clarify my these doubts.

               

               

              Thanks & Regards

              • 4. Re:  Getting Two different results at same frequency .interactive vs DDRx Batch Mode
                sandeep.kumar

                Hi Cristian ,

                 

                I checked everything,selected same drivers in both cases but the result are not coming same, when i have simulated in DDRx Batch mode wizard i have got some different waveform

                and when i simulated interactively feeding frequecy 800Mhz (DDR3 Data rate = 1600 MT/s) in digital Oscilloscope then i got different waveform also the

                amplitude is getting reduced. why there is amplitude reduction in the Data Signal.

                 

                 

                Kindly reply.

                • 5. Re:  Getting Two different results at same frequency .interactive vs DDRx Batch Mode
                  cristian.filip

                  If you are really using the same settings (operating frequency/data rate, driver strength, corner case, ODT, and probing location for same pair of transmitters/receivers) you should get the same results as the simulation engine is the same. Often additional terminations that were added in the quick terminator are responsible for reduced amplitude while interactively simulating. Check that out and if it is not the case I would suggest you to open a SR at Mentor as without a copy of the database is difficult to debug.

                  • 6. Re:  Getting Two different results at same frequency .interactive vs DDRx Batch Mode
                    sandeep.kumar

                    In quick analysis report of cross talk analysis why the report shows

                    sum of two aggressor nets ?

                     

                    do we have to consider the single net value as crosstalk limit or

                    sum of two .

                     

                    Suppose i set a electrical threshold of 150mv

                     

                    on one net is it is 147 mv

                    other net it is 146 mv

                     

                    if i will look individually then they are with in cross talk limit  but in report it is

                    showing the sum of above two (147 +146) = 293 mv crossing the threshold crosstalk?

                     

                    which one i have to consider individual one or sum of two ?

                     

                    also tell me how to decide the Electrical crosstalk of a given board?

                     

                    Thanks in advance

                    • 7. Re: Getting two different results at same frequency .interactive vs DDRx Batch Mode
                      agxinmj

                      hai

                            1.can i now the line you simulated is single ended or differential?

                            2.the waveform you get not only depends on the frequency it depends on the probe arrangement you establish  for differential signals in an oscilloscope

                            3.the ddr driver model settings and the ODT settings

                            4. the ddr as well as the controller has some ODT settings which will be available as submodels in model selector in the model ,for a good model

                      with odt function defined in the model you have to select and find the best combination of odt for read as well as write operation

                      5.check if it is a differential driver ,output and output inverted settings are same for both freq ,termination schemes are correctly chosen,input output settings of tx and rx model are correct

                      6.I found in my simulation both the results are found ok ,please provide the waveforms for both batch and normal it will help a lot in identifying the problem

                       

                       

                      regards

                      AGXIN.J