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MrEngineer
Visitor
Visitor
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Registered: ‎06-20-2021

[Synth 8-3295] tying undriven pin inst:sl_iport0[35] to constant 0 on virtual IO.

I have included virtual I/O block in block design.

vio_0 - only has output.

vio_1 - has only inputs

vio_2 - has only input.

Both vio_0 and vio2 on out of context synthesis give following warning.

37 x [Synth 8-3295] tying undriven pin inst:sl_iport0[36] to constant 0 

37 x [Synth 8-3295] tying undriven pin inst:sl_iport0[36] to constant 0

I have looked at https://www.xilinx.com/search/support-keyword-search.html#q=Synth%3A8-3295

What does this warning mean? This block is automatically generated.

 

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anusheel
Moderator
Moderator
187 Views
Registered: ‎07-21-2014

Hi @MrEngineer<,

It means either the pin has no connection or the connected logic was removed by the tool and hence the tool is tying the pin to '0'. 

Thanks
Anusheel 

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MrEngineer
Visitor
Visitor
176 Views
Registered: ‎06-20-2021

Thank you for taking time to respond.

I understand what the message says. Here's block diagram. VIO are connected. I am trying to understand why this message.

MrEngineer_0-1624296252033.png

 

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anusheel
Moderator
Moderator
114 Views
Registered: ‎07-21-2014

HI @MrEngineer ,

I was able to reproduce the issue by adding VIO in the design:

Finished Final Netlist Cleanup
---------------------------------------------------------------------------------
WARNING: [Synth 8-3295] tying undriven pin inst:sl_iport0[36] to constant 0
WARNING: [Synth 8-3295] tying undriven pin inst:sl_iport0[35] to constant 0
WARNING: [Synth 8-3295] tying undriven pin inst:sl_iport0[34] to constant 0
WARNING: [Synth 8-3295] tying undriven pin inst:sl_iport0[33] to constant 0
WARNING: [Synth 8-3295] tying undriven pin inst:sl_iport0[32] to constant 0

Looks like these messages are coming from the VIO core RTL and can be ignored safely. 

Thanks
Anusheel 

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