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转载于http://docs.huihoo.com/covered/user-manual/005.html Suppose that a DUT was comprised of the following module | |||
module test; | |||
The register called "a", after being simulated, would have achieved a total toggle percentage of 50% (or 3 out of 6). Can you see which toggles are missing? | |||
Bit 0 has never toggled to 1 (and has never been at a value of 1 and toggled to 0); therefore, bit-0 has toggled 0% (0 out of 2). Bit 1 has toggled from a value of 0 to 1, but has not toggled from a value of 1 to 0; therefore, bit-1 has toggled 50% (0 out of 2). Bit 2 is the only bit that has fully toggled, achieving a toggle percentage of 100% (2 out of 2). If you add all of the possible toggles to the number of achieved toggles, you end up with 3 out of 6 (or 50% total toggle coverage). | |||
Recommendations |
For a design to pass full coverage, it is recommended that the toggle coverage for all modules in a design received 100% coverage. If a bit is never changes value, it is usually an indication that a mode is not being exercised in the design or a datapath has a stuck-at issue. |