The following DCI outputs do not require reference resistors on VRN and VRP:
NOTE: There is no standard available for LVDS DCI output I/O. See Note 1 in the resolution section for more information.
The following inputs do not require reference resistors on VRP and VRN:
There is no termination on these inputs. An LVDCI_25 input is the same as a LVCMOS25 input.
Does this mean that VRN and VRP can be used as general I/O in a bank that contains these outputs?
Yes. For the inputs and outputs listed above, DCI termination is not used. Consequently, you can use the VRN/VRP as regular I/O. These input and output buffers are available as naming conventions only to match them with their respective outputs and inputs.
If you choose to use VRN and VRP as general I/O, make sure that the DCI I/O standards listed above are the only DCI standards (input or output) in the appropriate bank.
1. More information is available in the Spartan-3 Data sheet located at:
2. The 25 ohm resistor in series with the SSTL2_I_DCI outputs is not DCI-controlled.
3. You should always perform IBIS simulation to verify the signal integrity on any PCB trace. You can download Xilinx IBIS models at: