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AR# 12667

Virtex-II/-II FPGA Pro, Virtex-4 FPGA DCM - What is the output jitter for the CLKFX? (Jitter Calculator)


What is the output jitter for the CLKFX? The parameter CLKOUT_PER_JITT_FX is listed in the Data Sheet under DC and Switching Characteristics -> DCM Timing Parameters (or Output Clock Jitter). However, the value is not listed.

NOTE: You can access the data sheets at:



The CLKFX jitter value depends on the frequency, the CLKFX_MULTIPLY (M) value, and the CLKFX_DIVIDE (D) value.

To obtain the value for Virtex-II FPGA, Virtex-II Pro FPGA, or Virtex-4 FPGA, use the CLKFX Jitter Calculator which is available in the Architecture Wizard.

NOTE: Generally, using CLKDV or CLK2X allows better output jitter than using CLKFX.
AR# 12667
Date Created 08/29/2007
Last Updated 12/15/2012
Status Active
Type General Article
  • Virtex-II
  • Virtex-II Pro
  • Virtex-II Pro X
  • More
  • Virtex-II QPro/R
  • Virtex-4 FX
  • Virtex-4 LX
  • Virtex-4 QPro/R
  • Virtex-4 SX
  • Less
  • Digital Clock Manager (DCM) Module