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Altera_Forum
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13 years ago

AUTO_DELAY_CHAINS and source synchronous DDR interfaces

If you're spending hours and hours trying to figure out why your DDR source synchronous (FPGA=transmitter) interface is not meeting hold time to your interface's generated clock, you might try the following QSF/TCL assignment:

set_global_assignment -name AUTO_DELAY_CHAINS OFF

Wonders may ensue.

It seems that the fitter's output pin delay algorithm is:

A. Increase delay through the clock buffer until setup time is ridiculously easy to meet

B. Forget that you added this monstrous delay when you can't meet hold time
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