Why is ODT asserted for more than one rank in my DDR3 UniPHY controller?

Description

If you have a multi-rank DDR3 UniPHY controller generated in the Quartus® II software version 12.1SP1 or later, you may see the ODT signals for multiple ranks assert simultaneously.

There is a problem with ODT when the Memory format in the Memory Parameters tab of the MegaWizard™ Plug-In Manager is set to Discrete Device.

Resolution

The workaround is to change the Memory Format in the Memory Parameters tab to UDIMM.

This problem is fixed starting with the Quartus® II software version 15.0.