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AR# 35689

ModelSim SE 6.5c causing incorrect phase fuctionality with PLL

Description


There is a known issue when simulating ModelSim SE 6.5c and the UNISIM PLL model.

If you configure CLKOUT0 and CLKOUT1 of the PLL equally but add a 180 degree phase shift to CLKOUT1, the phase shift is not reflected in the simulation.

u_pll_adv : PLL_ADV
...
CLKOUT0_DIVIDE => value,
CLKOUT1_DIVIDE =>value,
....
CLKOUT0_PHASE => 0.000,
CLKOUT1_PHASE => 180.000,

Solution


This is a known issue specific to ModelSim 6.5c.

Workaround 1:
 
Add the "-novopt" option to the vsim command with ModelSim SE 6.5c.

Workaround 2:
 
Use a different version of ModelSim, for example ModelSim SE 6.6a.
AR# 35689
Date Created 05/14/2010
Last Updated 09/24/2014
Status Active
Type Known Issues
Devices
  • Spartan-6 LX
  • Spartan-6 LXT
  • Virtex-6 CXT
  • More
  • Virtex-6 HXT
  • Virtex-6 LX
  • Virtex-6 LXT
  • Virtex-6 SXT
  • Less
Tools
  • ISE Design Suite - 11.5
  • ISE Design Suite - 12.1