AR# 34219

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Virtex-6 MMCM - Cascaded MMCMs may not work in hardware

Description

In the Virtex-6 FPGA,cascaded MMCMs may not work in hardware. The behavior seen is that the second MMCM in the chain does not lock.

Solution

The ISEimplementationsoftware automatically selects the COMPENSATION mode for thecascaded MMCM. In some cases, the software does not set this attribute correctly.The workaround to this issue is to manually set theCOMPENSATIONattribute to CASCADE for the second MMCM in the user design. This issue will be fixed in ISE 12.4 software.
AR# 34219
Date 05/19/2012
Status Active
Type Known Issues
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