In HSPICE simulation of some SelectIO (e.g., differential HSTL output), there are some warnings in the ".lis" file.
For example, while running the default simulation for the Virtex-5 HSTL differential output diffhstl1.sp, I find that the .lis file reports the following warning:
"**warning** only 1 connection at node 42 and 43:d<*> defined in subckt sim_ddr_mux_mode
: called in element 42:r7<0> defined in subckt sim_ddr_mux_mode at line 493
within the hspice source, library or include file"
The simulation result is correct. What is the root cause of the warning?
These warnings can be safely ignored.
The warnings occur because a generic test bench resides under the driver or receiver models, and this test bench must work for all I/O standards. Therefore, there are many control nets coming out of the test bench, and not all of them are used by all I/O standards.