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AR# 31734

MIG v2.3 - Spartan-3 Generation DDR2 SDRAM: tRAS and tRFC specifications are violated for certain memory parts


The MIG v2.3 Spartan-3 Generation DDR2 SDRAM design violates the tRAS and tRFC specifications for certain memory parts because the parameters are currently fixed values.  

This issue will be resolved in MIG v3.0.


tRAS Violation 

MIG v2.3 and all prior versions use a fixed value for the tRAS parameter. 

The parameter is set to 7 times the clock period. 

The maximum clock period supported for Spartan-3 Generation DDR2 is 166 MHz, resulting in a maximum tRAS of 42 ns. 

If a memory device has a tRAS specification greater than 42 ns (as some Qimonda devices do), the violation will occur. 

The violation will occur only for single read with a burst length of 4.  


tRFC Violation 

MIG v2.3 and all prior versions have a maximum supported value for tRFC of 240 ns during initialization.

If the tRFC value for the memory device is greater than 240 ns, violations will occur during the memory initialization. 


If you need a work-around for this issue before the release of MIG v2.4, please open a WebCase at: 


AR# 31734
Date Created 09/24/2008
Last Updated 08/18/2014
Status Active
Type General Article
  • Spartan-3
  • Spartan-3 XA
  • Spartan-3A
  • More
  • Spartan-3A DSP
  • Spartan-3AN
  • Spartan-3E
  • Less
  • MIG