different voltages in IO Differencial ports

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abimann

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I use XC4VLX100 , used buffers for HDMI output OBUFDS/OBUFTDS, in UG070.PDF said Virtex-4 can use IOSTANDARD LVDS_25, LVDSEXT_25, ULVDS_25,
I used all of them but cannot pass implementation stage in ISE, but board used 3.3V only, it mean chip can check voltage ? and if I use external 2.5 V it must work ?

board designers guid :
Please note that you must use I/O standard “LVCMOS33” or “LVTTL”, when IO voltage is 3.3V. If you need to use other I/O standard, then, cut away J6 and J7, and connect external I/O voltage

ISE says :

ERRORack:1107 - Pack was unable to combine the symbols listed below into a
single IOBS component because the site type selected is not compatible.
 
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You didn't mention the exact board type, thus we can't know which IO banks are supplied by "J6 and J7".

ISE checks if all IOs of a bank are declared to use the same voltage. The FPGA can't check the actual voltage, but using a voltage outside specifications (e.g. operating LVDS_25 with 3.3V supply) will at least degrade the performance or cause malfunction.
 

I found problem , clock capable low capacitance ports cannot used i changed ports and that's pass implementation .. thank for all
 
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