AR# 38656


14.1 PlanAhead - I/O port xxx is Single-Ended but has an IOStandard of xxx which can only support Differential


I created a one pin planning project in the PlanAhead tool by importing the UCF file, but DRC reports the following error:

I/O port my_port_p is Single-Ended but has an IOStandard of DIFF_SSTL_18_II which can only support Differential 

The I/O port is intended for differential.

How can I resolve this error?


PlanAhead 14.1 and earlier tool versions were not able to infer a differential pair based on signal names with _p and _n suffixes. This required the user to manually define them as a differential pair.

To define a differential pin pair, select the desired two I/O ports, and select the Make Diff Pair pop-up menu command in the I/O Ports view.

In PlanAhead 14.2 and later tool versions, the tool infers differential ports based on the following rules:

  • A Differential pair is inferred any time two ports with the same differential I/O standard and the same direction have names whose only difference is a single character that is "n" in one port and "p" in the other.
  • Additionally, if one of the ports is placed, the other port must be placed on the pin that is the differential pair of the first port's pin, and the pin whose name has the "p" is placed on the P-type pin.
AR# 38656
Date 11/04/2013
Status Archive
Type General Article
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