Webench Interface Designer - DS125RT410 simulation bug

Hi Kawai-san,

Based on my understanding of our IBIS-AMI model, you are partially correct. In a realistic scenario, the CDR would be unable to recover the clock from the incoming data to acquire lock. This is due to significant attenuation, particularly at bits that transition at the Nyquist frequency. Therefore, with a real part, when the CDR is unable to lock, then the retimer output is muted. Therefore, I do not expect the retimer to produce the clean eye. I actually would expect the output waveform to be muted.

However, after reviewing the DS1xxDF410/DS1xxRT410 model documentation, it looks like the model performs the CTLE + DFE optimization, but ultimately, the output will make some kind of slicing decision to declare each bit as either a "1" or "0", regardless of whether the CDR would actually achieve lock in a realistic scenario. This is not necessarily a bug in Webench Interface Designer as this is a limitation of IBIS-AMI models in general.

When using the IBIS-AMI retimer model, it is often more important to look at the output directly after the CTLE + DFE than the Tx output of the retimer. It is important to ensure that the equalized eye that the CDR sees internally is as open as possible.

Thanks,

Michael