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AR# 34368

Virtex-5 - Why does the maximum delay possible from the IODELAY vary?

Description

When I look at the maximum achievable delay on a board using the maximum number of taps in the IODELAY, the delay is not necessarily 78 ps x 64 Taps.

Solution


When using the IODELAY, TRACE should be used to get an idea of the MIN, MAX, and TYPICAL delays possible.
The following are for a FIXED IDELAY with a tap setting of 0 and 63.

Using the MIN timing:




So the Minimum Delay is 6.162nS - 1.535nS = 4.627nS.

Using the MAX timing:



The MAX delay is 6.752nS - 1.535nS = 5.217nS

So, the IODELAY maximum range is between4.627nS and5.217nS, or 4.922nS +/- 295pS.
AR# 34368
Date Created 07/19/2010
Last Updated 12/15/2012
Status Active
Type General Article
Devices
  • Virtex-5 FXT
  • Virtex-5 LX
  • Virtex-5 LXT
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  • Virtex-5 SXT
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  • Virtex-5Q
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