cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
nag.chil
Observer
Observer
4,366 Views
Registered: ‎03-29-2016

Spartan 3 FPGA LVCMOS18

Sir,

 I need to drive 1.8V from Spartan 3 FPGA. I followed as per spartan 3 constraints file. Even though i got the following warnigs and I received 3.3V.

WARNING:XdmHelpers:376 - Unexpected value of "LVCMOS18" found for attribute DRIVE. Unable to convert this to the expected numeric value.
WARNING:Xst:37 - Detected unknown constraint/property "DRIVE". This constraint/property is not supported by the current software release and will be ignored.

 

lvcmos.JPG
0 Kudos
Reply
6 Replies
austin
Scholar
Scholar
4,348 Views
Registered: ‎02-27-2008

n,

 

In addition to setting the IO standard, you must supply 1.8 volts to the Vcco pins for that bank.

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
0 Kudos
Reply
nag.chil
Observer
Observer
4,324 Views
Registered: ‎03-29-2016

To set the Vcco 1.8V, Do i need to supply externally or enter the command in constraint file?

0 Kudos
Reply
austin
Scholar
Scholar
4,309 Views
Registered: ‎02-27-2008

Both,

 

Hardware must be connected to 1.8v for that bank, and constraints must match.

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
0 Kudos
Reply
gnarahar
Moderator
Moderator
4,273 Views
Registered: ‎07-23-2015

@nag.chil The setting in the constraint is to let the FPGA fabric know what the expected voltage and IO Standard is so that it can use the respective Voltage thresholds for Inputs and be able to drive with the respective drive strength in case of Outputs. 

 

As Austin mentioned, both the Hardware and your constraint should be in sync. 

- Giri
--------------------------------------------------------------------------------------------------------------------
There's no such thing as a stupid question. Feel free to ask but do a quick search to make sure it ain't already answered.
Keep conversing, give Kudos and Accept Solution when you get one.
-----------------------------------------------------------------------------------------------------------------------
0 Kudos
Reply
nag.chil
Observer
Observer
4,181 Views
Registered: ‎03-29-2016

Yeah Thank you guys ...

I understood what it is....

 

So now can u say, in hardware side how can i connect my spartran-3 FPGA bank to 1.8V .......

Any document on that....??

0 Kudos
Reply
gnarahar
Moderator
Moderator
4,176 Views
Registered: ‎07-23-2015

@nag.chil Connect the VCCO of that Bank to a 1.8V Power Rail on your board. 

- Giri
--------------------------------------------------------------------------------------------------------------------
There's no such thing as a stupid question. Feel free to ask but do a quick search to make sure it ain't already answered.
Keep conversing, give Kudos and Accept Solution when you get one.
-----------------------------------------------------------------------------------------------------------------------
0 Kudos
Reply