coverage

cited from http://www.ovmworld.org/forums/showthread.php?t=121
Code coverage: This will give information about how many lines are exected, how many times expressions, branches executed. This coverage is collected by the simulation tools. Users use this coverage to reach those corner cases which are not hit by the random testcases. Users have to write the directed testcases to reach the missing code covearage areas.

Functional coverage: This coverage will be defined by the user. User will define the coverage points for the functions to be covered in DUT. This is completly under user control. like covergroup definition defined in SV

Both of them have equal importance in the verification. 100% functional coverage does not mean that the DUT is completly exercised and vice-versa. Verification engineers will consider both coverages to measure the verifcation progress.

Coverage tool
All the HVL simulators have Functional Coverage tool with it.You have to write coverage code and then switch ON the coverage during simulation.
And use a coverage viewing tool (again, the same EDA company will have it) to view the coverage.
For Cadence IES/IUS:
1. For switching coverage ON:Use +nccovfile+dut_cov.txt while compiling.
The content of dut_cov.txt is:
select_coverage -all -module top
...
select_functional
select_fsm
During simulation use:-covoverwrite -covtest mycov.cov
2. To view coverage:
Do:
iccr -keywords+detail iccr.cmd
or:
iccr -keywords+summary iccr.cmd
or:
iccr -keywords+dontmerge iccr.cmd
The respective content of iccr.cmd is:
load_test cov_work/design/*merge * -output ALL
reset_coverage
load_test cov_work/design/ALL
report_detail -instance -betsafd -cgopt top... > detail.rpt

load_test cov_work/design/*merge * -output ALL
reset_coverage
load_test cov_work/design/ALL
report_summary -instance -cgopt top... > summary.rpt

load_test cov_work/design/*
report_summary -instance -cgopt top... > summary.rpt

There is a coverage quick start guide included with IUS as well in order to get you started. Search for "icc quick start guide" in cdnshelp