I am trying to understand what "bad signal " means and how to fix this error?
The "Bad Signal" message usually means that the waveform is not clean enough or aligned enough for the program to make a valid measurement. The signal waveform must cross the appropriate high or low, DC or AC threshold at the receiver pin in order to have a valid timing measurement. The first step in debugging this problem is to click on the Bad Signal link to see the waveforms. You need to have selected the option to save waveforms in the DDRx Wizard before running the batch simulations. From the waveforms, you can see if the problem is caused by reflections (ringback in the waveform) or by misaligned address and clock signals. From the other data in your image, it appears that the A0 trace is a bit short compared to the associated clock net.
if you doubleclik on the link "bad signal" you may get more info.
A single click is sufficient. The report is an HTML document and the Bad Signal text is a hyperlink.
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