10 Replies Latest reply on Apr 4, 2013 1:33 PM by Ed Bartlett

    Clock ticks not generated error

    Bruce

      Hi Expert,

       

      I encountered this error message when runing the IBIS-AMI channel analyzer, can you help to explain:

      1. What's the clock ticks?

      2. Is it a must or optional item?

      Thanks.

        • 1. Re: Clock ticks not generated error
          david.a.duncan

          I am seeing the same error, but your attached graphic did not show the error dialog, so I have attached it here.

          • 2. Re: Clock ticks not generated error
            Bruce

            Hi David,

             

            Yes, that is what I met. Thanks.

             

            Is there any Mentor guy can answer these questions?

            • 3. Re: Clock ticks not generated error
              Ed Bartlett

              Hello Zhenshui and David,

               

              - The clock ticks (times) are generated by the clock data recovery (CDR) loop of the receiver model (RX). They show the times where the sampler controlled by the output of CDR should read discrete values from the continuous output waveform. (According to AMI specification, we take a clock time value, deemed to designate a start of a new bit - as seen by Rx model – then add ½ of the bit time to it and get the moment where the waveform should be sampled. This point of the waveform is aligned with the center of the eye diagram).

               

              - Most of the existing Rx AMI models return an array of clock times after calling their GetWave() function. Some of them however may not return the clocks (providing empty clock data), in which case the behavior of the Rx CDR is not modeled. Such behavior is allowed, therefore it’s not an error (the popup is a warning to the user). However, inability to model CDR may affect the validity of the simulation results.

               

              - If the Rx AMI does not generate clock times, as detected after several GetWave calls, Hyperlynx (starting from version 8.2) enables an internal CDR inside the simulator (not the one in Rx AMI) with a purpose to properly center the eye/BER.

               

              - Since we cannot be sure that HyperLynx’s internal CDR behaves identically to the actual receiver, the warning is generated. In this case, getting an open eye doesn’t always imply that the model is a good model. It can also imply that an error in the model has been ignored and that the eye is probably based on the something less realistic or ideal.

               

              Best regards,

              Ed.

              • 4. Re: Clock ticks not generated error
                Bruce

                Hi Ed,

                 

                Thanks for your great explaination.

                 

                So if we use a perfect CDR(Mentor buildin) to replace the actual one and do the simulation, the result must be difference with the actual situation. It means we can't use it at all. Am i right?

                It that's the case, what should I do in order to get a reliable result? To get a new AMI model from vendor or any other workaround?

                 

                Best Regards,

                Bruce

                • 5. Re: Clock ticks not generated error
                  Ed Bartlett

                  Hello Bruce,

                          The results you get may or may not be optimistic. They still can be very useful for your investigations until you get a more complete model.  I recommend asking the vendor for a more complete Rx AMI model. We will work with the model developers if that is useful to them.

                  Best regards,
                  Ed.

                  • 6. Re: Clock ticks not generated error
                    shimon.mordooch

                    Hello Ed,

                     

                    I have found your folowing answer on the web:

                     

                    "- The clock ticks (times) are generated by the clock data recovery (CDR) loop of the receiver model (RX). They show the times where the sampler controlled by the output of CDR should read discrete values from the continuous output waveform. (According to AMI specification, we take a clock time value, deemed to designate a start of a new bit - as seen by Rx model – then add ½ of the bit time to it and get the moment where the waveform should be sampled. This point of the waveform is aligned with the center of the eye diagram).

                     

                    - Most of the existing Rx AMI models return an array of clock times after calling their GetWave() function. Some of them however may not return the clocks (providing empty clock data), in which case the behavior of the Rx CDR is not modeled. Such behavior is allowed, therefore it’s not an error (the popup is a warning to the user). However, inability to model CDR may affect the validity of the simulation results.

                     

                    - If the Rx AMI does not generate clock times, as detected after several GetWave calls, Hyperlynx (starting from version 8.2) enables an internal CDR inside the simulator (not the one in Rx AMI) with a purpose to properly center the eye/BER.

                     

                    - Since we cannot be sure that HyperLynx’s internal CDR behaves identically to the actual receiver, the warning is generated. In this case, getting an open eye doesn’t always imply that the model is a good model. It can also imply that an error in the model has been ignored and that the eye is probably based on the something less realistic or ideal."

                     

                    We are using a sub-contructor for simulations and having the same problem.

                    I sent your answer to our sub-contractor, but they doesnt know how to use the internal CDR inside the simulator instead the RX AMI one.

                     

                    Could you please guide us step by step on how to do it or sugest how to solve the problem?

                    How far from reality the results are from your experiance?

                     

                    Thanks,

                    Shimon

                    • 7. Re: Clock ticks not generated error
                      Ed Bartlett

                      Hello Shimon,

                       

                       

                           For your questions:

                       

                      I sent your answer to our sub-contractor, but they doesnt know how to use the internal CDR inside the simulator instead the RX AMI one.

                       

                      1. Could you please guide us step by step on how to do it or sugest how to solve the problem?

                      2. How far from reality the results are from your experiance?

                       

                          Answer: 

                       

                      1. The internal CDR is not controllable by the user. In the case that the Rx AMI does not generate clock times, HyperLynx (starting from version 8.2) enables an internal CDR inside the simulator by itself, and builds the eye using that.

                      2. This is really a question for the model maker, since the model maker made the decision not to generate clock ticks. HyperLynx does what should be done in this case according to the AMI specification, as described earlier.

                       

                      I hope this helps you out.

                       

                      Best regards,

                      Ed.

                      • 8. Re: Clock ticks not generated error
                        shimon.mordooch

                        Hi Ed,

                        Thanks for the quick response.

                        If we dis-regard this error, we encounter a problem that when they run Sweep on tap values, this error jump per each run and need some to press OK, instead letting the PC to run over night.

                         

                        Is there a way to ignore the error and let the SW to run till it ends?

                         

                        Shimon

                        • 9. Re: Clock ticks not generated error
                          shimon.mordooch

                          Hi Ed,

                           

                          Thanks for the quick response.

                           

                          If we dis-regard this error, we encounter a problem that when they run Sweep on tap values, this error jump per each run and need some to press OK, instead letting the PC to run over night.

                           

                           

                           

                          Is there a way to ignore the error and let the SW to run till it ends?

                           

                           

                           

                          Shimon

                          • 10. Re: Clock ticks not generated error
                            Ed Bartlett

                            Hello Shimon,

                                     Unfortunately I don't have a solution in the version that you are using. This issue is defect report  846275, and it is currently planned to be fixed in the next release of HyperLynx (version 9.0). My apologies for the inconvenience.

                            Best regards,
                            Ed.