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AR# 23348

10.1 Timing Analyzer - Why does the data sheet section indicate a different PERIOD number?

Description

When I constrain the input clock of DCM and use its output clocks to drive the design, I notice different results between the data sheet section and the timing constraints report. Why does this occur?

Solution

This is a limitation of the data sheet report; it does not take into account "multiplied by and duty cycle correction" which is derived for DCM's output. Below is an example: 

 

================================================================================ 

Timing constraint: PERIOD analysis for net "dcm_clk200/clkfx_dcm" derived from 

net "buf_clk200" PERIOD = 4.95 ns HIGH 50%  

INPUT_JITTER 0.15 ns; 

multiplied by 2.00 and duty cycle corrected to 9.900 nS HIGH 4.950 nS  

 

If the timing constraint does not have this content, the data sheet report and timing constraint report will have the same PERIOD number.  

 

This issue will be fixed in a future release.

AR# 23348
Date Created 09/04/2007
Last Updated 05/20/2014
Status Archive
Type General Article