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VHDL VITAL SDF

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Standard Delay Format (SDF) Timing Annotation ModelSim EE/PLUS Reference Manual

Errors and warnin

Errors issued by the SDF annotator while loading the design prevent the

simulation from continuing, whereas warnings do not. Use the

-sdfnoerror

option

with

vsim

(p91) to change SDF errors to warnings so that the simulation can

continue. Warning messages can be suppressed by using

vsim

with either the

-sdfnowarn

+nosdfwarn

options.

Another option is to use the

SDF

page from the

Load Design

dialog box (shown

above). Select

Disable SDF warnings

(-sdfnowarn, or +nosdfwarn) to disable

warnings, or select

Reduce SDF errors to warnings

(-sdfnoerror) to change

errors to warnings.

See "Troubleshooting" (p448) for more information on errors and warnings, and

how to avoid them.

VHDL VITAL SDF

VHDL SDF annotation works on VITAL cells only. The IEEE 1076.4 VITAL

ASIC Modeling Specification describes how cells must be written to support SDF

annotation. Once again, the designer does not need to know the details of this

specification because the library provider has already written the VITAL cells and

tools that create compatible SDF files. However, the following summary is

provided to help understand simulator error messages in case of user error or in

case the vendor’s SDF does not match the VITAL cells. For additional VITAL

specification information see "Obtaining the VITAL specification and source

code" (p432).

SDF to VHDL

eneric matchin

An SDF file contains delay and timing constraint data for cell instances in the

design. The annotator must locate the cell instances and the placeholders (VHDL

generics) for the timing data. Each type of SDF timing construct is mapped to the

name of a generic as specified by the VITAL modeling specification. The

annotator locates the generic and updates it with the timing value from the SDF

file. It is an error if the annotator fails to find the cell instance or the named

generic. The following are examples of SDF constructs and their associated

generic names: