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Standard Delay Format (SDF) Timing Annotation
Verilog SDF
The SDF statement CONDELSE, when targeted for Vital cells, is annotated to a tpd generic of
the form tpd_<inputPort>_<outputPort>.
Resolving Errors
If the simulator finds the cell instance but not the generic then an error message is issued. For
example,
** Error (vsim-SDF-3240) myasic.sdf(18):
Instance ’/testbench/dut/u1’ does not have a generic named ’tpd_a_y’
In this case, make sure that the design is using the appropriate VITAL library cells. If it is, then
there is probably a mismatch between the SDF and the VITAL cells. You need to find the cell
instance and compare its generic names to those expected by the annotator. Look in the VHDL
source files provided by the cell library vendor.
If none of the generic names look like VITAL timing generic names, then perhaps the VITAL
library cells are not being used. If the generic names do look like VITAL timing generic names
but don’t match the names expected by the annotator, then there are several possibilities:
•
•
The vendor’s tools are not conforming to the VITAL specification.
•
The vendor’s library and SDF were developed for the older VITAL 2.2b specification.
This version uses different name mapping rules. In this case, invoke vsim with the
-vital2.2b option:
The SDF file was accidentally applied to the wrong instance. In this case, the simulator
also issues other error messages indicating that cell instances in the SDF could not be
located in the design.
vsim -vital2.2b -sdfmax /testbench/u1=myasic.sdf testbench
For more information on resolving errors see Troubleshooting.
Verilog SDF
Verilog designs can be annotated using either the simulator command line options or the
$sdf_annotate system task (also commonly used in other Verilog simulators). The command
line options annotate the design immediately after it is loaded, but before any simulation events
take place. The $sdf_annotate task annotates the design at the time it is called in the Verilog
source code. This provides more flexibility than the command line options.
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ModelSim User’s Manual, v10.1c