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AR# 44706

Spartan-6 PLL - Clock phase in the INTERNAL Mode

Description

If using the Spartan-6 FPGA PLL in INTERNAL compensation mode, what is the phase relationship between the CLKIN and the CLKOUT ports?

Solution

If you are using a PLL in the INTERNAL mode, make sure to use the PLL for frequency synthesis only. The PLL does not perform any phase-alignment or deskewing of the clock. Because of this, the phase relationship between the two clocks is not guaranteed and cannot be determined.

If the design requires that a known phase relationship be used with the PLL, use of the INTERNAL compensation mode is not recommended. In this case, use either SYSTEM_SYNCHRONOUS or SOURCE_SYNCHRONOUS, which have a known phase relationship between the input and output clock ports of the PLL.

Linked Answer Records

Associated Answer Records

Answer Number Answer Title Version Found Version Resolved
46790 Spartan-6 FPGA Design Assistant - Troubleshooting Common Clocking Problems N/A N/A
AR# 44706
Date Created 11/04/2011
Last Updated 12/15/2012
Status Active
Type General Article
Devices
  • Spartan-6 LX
  • Spartan-6 LXT
  • Spartan-6Q