cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
daniel.cogan
Explorer
Explorer
4,425 Views
Registered: ‎07-30-2013

lpddr2 example design doesn't calibrate

Jump to solution

I have a standalone (example) lpddr2 design which doesn't complete calibration.  It seems to start read leveling and complete read leveling, but has no error, and doesn't complete calibration.  From what I can make of ug586 (which doesn't specifically address lpddr2 debug), read leveling is the final stage of calibration.  So, I'm confused how it can finish the stage with no error yet not finish calibration.  Any insights?

 

I've included the debug in the controller design, but need help making sense of the debug output.  

 

 

I'm attaching a project archive and .ila (exported ila data).  Please advise.

Dan

0 Kudos
1 Solution

Accepted Solutions
daniel.cogan
Explorer
Explorer
7,155 Views
Registered: ‎07-30-2013

The solution to my problem was to use internal vref (checkbox in the MIG).

I don't know why this is the case as the external vref circuit looked fine, but will ask this as a separate question...

 

View solution in original post

0 Kudos
2 Replies
daniel.cogan
Explorer
Explorer
4,248 Views
Registered: ‎07-30-2013

As an update:
The calibration actually completes 25% of the time.  When it completes, pattern generation test passes too.  Any ideas on why a controller would calibrate sometimes?

 

Comparing the ILA output from a passing and failing case, the second stage of read leveling never starts, but no error on stage 1.  Based on the flowchart on pg 595 of UG586, this suggests the problem could be in Read Valid Calibration. (I'm assuming stage 2 read leveling in LPDDR2 is actually PRBS leveling).  I haven't found any information as to how to debug/fix valid calibration issues.  But at least to verify that this IS the issue, I intend to add signals from the ddr_phy_rdlvl.v to chipscope.  Unfortunately, this state is not part of the built-in MIG debug, presumably because it's not used in DDR3.

 

Any ideas on how to debug read valid calibration issues? (or what causes it)

 

 

 

 

 

0 Kudos
daniel.cogan
Explorer
Explorer
7,156 Views
Registered: ‎07-30-2013

The solution to my problem was to use internal vref (checkbox in the MIG).

I don't know why this is the case as the external vref circuit looked fine, but will ask this as a separate question...

 

View solution in original post

0 Kudos