ModelSim SE User's Manual - Electrical and Computer Engineering

UM-334 13 - Measuring code coverage
Introduction
Usage flow for code coverage
ModelSim SE User’s Manual
ModelSim code coverage gives you graphical and report file feedback on which statements,
branches, conditions, and expressions in your source code have been executed. It also
measures bits of logic that have been toggled during execution.
With coverage enabled, ModelSim counts how many times each executable statement,
branch, condition, expression, and logic node in each instance is executed during
simulation. Statement coverage counts the execution of each statement on a line
individually, even if there are multiple statements in a line. Branch coverage counts the
execution of each conditional "if/then/else" and "case" statement and indicates when a true
or false condition has not executed. Condition coverage analyzes the decision made in "if"
and ternary statements and is an extension to branch coverage. Expression coverage
analyzes the expressions on the right hand side of assignment statements, and is similar to
condition coverage. Toggle coverage counts each time a logic node transitions from one
state to another.
Coverage statistics are displayed in the Main, Objects, and Source windows and also can
be output in different text reports (see "Reporting coverage data" (UM-350)). Raw coverage
data can be saved and recalled, or merged with coverage data from the current simulation
(see "Saving and reloading coverage data" (UM-354)).
ModelSim code coverage offers these benefits:
It is totally non-intrusive because it’s inte grated into the ModelSim engine – it doesn’t
require instrumented HDL code as do third-party coverage products.
It has very little impact on simulation performance (typically 5 to 10 percent).
It allows you to merge sets of coverage data without requiring elaboration of the design
or a simulation license.
The following is an overview of the usage flow for simulating with code coverage. More
detailed instructions are presented in the sections that follow.
1 Compile the design using the -cover bcest argument to vcom (CR-311) or vlog (CR-358).
2 Simulate the design using the -coverage argument to vsim (CR-373).
3 Run the design.
4 Analyze coverage statistics in the Main, Objects, and Source windows.
5 Edit the source code to improve coverage.
6 Re-compile, re-simulate, and re-analyze the statistics and design.