AR# 14859

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5.1i, DCM Wizard - If I select the STARTUP_WAIT attribute, is it still necessary to set the LCK_cycle BitGen option?

Description

General Description:

The "Advanced" window of the DCM Wizard contains an option to "Wait for DCM lock before DONE signal goes High". When this is set to "Yes", the STARTUP_WAIT attribute is set to "TRUE". Is it still necessary to set the LCK_cycle BitGen option?

Solution

For the STARTUP_WAIT attribute to work correctly, not only must the attribute be set, but the configuration sequence must be modified by setting the BitGen "LCK_cycle" option. This will cause the configuration startup sequence to wait in the specified LCK_cycle until the DCM locks.

For more information, please see the "Using the Digital Clock Manager" section of the Virtex-II/Pro User Guide:

Virtex-II:

http://www.xilinx.com/xlnx/xweb/xil_publications_display.jsp?category=/Data+Sheets/FPGA+Device+Families/Virtex-II&iLanguageID=1
Virtex-II Pro:

http://www.xilinx.com/xlnx/xweb/xil_publications_display.jsp?category=/Data+Sheets/FPGA+Device+Families/Virtex-II+Pro&iLanguageID=1

The DCM Wizard does not currently include information about the additional BitGen option. In the 6.1i ISE software release, a warning in the DCM Wizard will alert you to this situation.

AR# 14859
Date 12/15/2012
Status Active
Type General Article
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