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Simulating Data Write/Read

Question asked by mm784 on Jul 10, 2020
Latest reply on Jul 28, 2020 by weston_beal

After I simulated a Data WRITE and imported the resulting waveforms DQ (8 bits)and DQs into the digital oscilloscope, I am seeing expected waveforms, with appropriate leveling to make DQS out of phase with DQ and transition at HIGH/LOW of DQ. So rising edges of DQS are aligned with DQ HIGH/LOW points. Only 1 DQS .csv file is generated to represent this shift.

 

However, for Data READ 2 .csv DQS files are generated. One is called 'before shift' and 2nd called 'after shift'. Now for read I am expecting the rising/falling edges of DQS be aligned with DQ rising/falling edges. This corresponds to the DQS waveform 'before shift' in BLUE. The GREEN waveform is for DQS 'after shift' and is aligned similar to a WRITE operation.

 

Please explain why 2.csv show up for READ, and 1 .csv for WRITE. Also, does 'after shift' represent the DQS waveform after leveling? If so, why would it be out of phase with DQ for READ?

 

Thank you

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