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AR# 15720

5.1i CPLD Hprep6 CoolRunner-II - VREF I/O Standards (HSTL-1, SSTL2-1, SSTL 3-1) are not working on the device


General Description: 

When I implement an I/O Standard that requires a VREF (HSTL-1, SSTL2-1, SSTL 3-1), the inputs do not function correctly on the device.


This problem is due to bug that occurs when the VREF pins are being terminated internally (either with bus-hold or with a weak pull-up). 


This problem is fixed in the latest 5.1i Service Pack, available at:  


The first service pack containing the fix is 5.1i Service Pack 3.

AR# 15720
Date Created 09/03/2007
Last Updated 05/08/2014
Status Archive
Type General Article