Chapter 14. Reading the Report
| Part III. Command-line Usage |

## Chapter 14. Reading the Report

This chapter describes the meanings of the textual report output that Covered generates when the report command is issued. It is well understood by the developers of Covered that a code coverage tool is only as good as the output that it generates, and this, of course, includes the ability to discern the information provided by the report.

To help describe the various sections of a Covered report, we will use a relatively small Verilog file containing our DUT, generating the two main types of reports (module and instance) based on the CDD generated for this file. This example file is provided here

After being compiled and run, this module is scored with the following Covered command:

`covered score -t main -v example.v -o example.cdd -vcd example.vcd`

The module-based verbose report can be viewed in its entirety example.rptM.html and is generated with the following command:

`covered report -d v example.cdd`

The instance-based verbose report can be viewed in its entirety here and is generated with the following command:

`covered report -i -d v example.cdd`

The instructions for analyzing each of the six types of coverage information from the report can be found on the following pages.

1. Section 14.1, “Reading Line Coverage”

2. Section 14.2, “Reading Toggle Coverage”

3. Section 14.3, “Reading Memory Coverage”

4. Section 14.4, “Reading Combinational Logic Coverage”

5. Section 14.5, “Reading FSM Coverage”

6. Section 14.6, “Reading Assertion Coverage”

For information on reading race condition information in the report, please see the user guide page detailing race conditions and viewing the reports.

## 14.1. Reading Line Coverage

### Summary Information Description - Module-based

For module-based reports, the summary table for line metrics includes information for the name of each module that was covered and the name of the file in which the module is described in. Lines 15 through 24 of the module-based report show what this information looks like in the report. We have three modules that were scored within our DUT: main, fsma and fsmb. The table shows that all three modules were described in the file "example.v".

### Summary Information Description - Instance-based

For instance-based reports, the summary table for line metrics includes information for the Verilog hierarchy pertaining to each instance on the left-hand-side of each row. Lines example.rptI.html#15 of the instance-based report show what this information looks like in the report. In our DUT example, there are three instances within the design with the Verilog hierarchies of "main", "main.fsm1" and "main.fsm2".

### Summary Information Description - Both

On the right-hand side of each row in the table are the hit, miss and total numbers for the line coverage, followed by a calculated percent of the lines that were hit (calculated by taking the number of lines hit during simulation divided by the total number of lines that Covered simulated). The hit value indicates how many lines were executed during the simulation; the miss value indicates the number of lines not executed during simulation; and the total value indicates the total number of lines within the specified module/instance that Covered was able to simulate.

If the percentage value in the far left of the summary table is 100%, this indicates that all lines that Covered was capable of simulating (for the module/instance of this row) were executed. If the value of the percentage is less than 100%, this indicates that some number of lines were not executed and full coverage was not achieved for that module/instance. Note that for a module/instance which does not contain any lines in which Covered was able to simulate, the values of hit, miss, and total will be 0 while the hit percentage value will indicate 100%.

### Verbose Information Description - Both

If the miss value for a particular module was not 0 (indicating that lines were missed during simulation) and the '-d v' option was specified on the command-line (specifying to output verbose reporting information), the line that was missed during simulation will be output below the summary information per module that contained missed lines. In our sample report, there was one line that was missed during simulation (according to the summary output) for the module called "fsmb" (instance "main.fsmb"). The line number and Verilog line that was missed is output in lines 25 through 29 of the module-based report and in lines 25 through 29 of the instance-based report.

If a module does not contain any missed lines and the '-d v' option was specified, no verbose output will be displayed for this module. Likewise, if a module/instance does not contain any lines that Covered could execute, no verbose output will be displayed.

| Note

The definition of what Covered considers a line is a statement (ex. assignment, conditional, etc.). If a statement is written in such a way that it consumes multiple file lines, Covered only counts the statement as one line. The user can assume that if the beginning of a statement is labeled as missed, the entire expression was missed (not just the first line of the expression). For example, consider the following code:

      always @(posedge b)
        a <= (b & c) |
             (d & e);

If the expression

      a <= (b & c) | (d & e);

is not executed during simulation, Covered will indicate that only one line was missed during execution (not two), and it will display the missing line (if verbose reporting is specified with the '-d v' option) as the following:

      2:      assign a <= (b & c) ...

The "..." notation at the end of the Verilog output indicates that the statement was a multiline statement in the source code but is only considered one line.

## 14.2. Reading Toggle Coverage

### Summary Information Description - Module-based

For module-based reports, the summary table for toggle metrics includes information for the name of each module that was covered and the name of the file in which the module is described in. Lines 41 through 51 of the module-based report show what this information looks like in the report. We have three modules that were scored within our DUT: main, fsma and fsmb. The table shows that all three modules were described in the file "example.v".

### Summary Information Description - Instance-based

For instance-based reports, the summary table for toggle metrics includes information for the Verilog hierarchy pertaining to each instance on the left-hand-side of each row. Lines 41 through 51 of the instance-based report show what this information looks like in the report. In our DUT example, there are three instances within the design with the Verilog hierarchies of "main", "main.fsm1" and "main.fsm2".

### Summary Information Description - Both

On the right-hand side of each row in the table are the hit, miss and total numbers for the toggle 0->1 coverage, followed by a calculated percent of the signal bits that toggled from a value of 0 to a value of 1 (calculated by taking the number of bits that toggled from 0 to 1 during simulation divided by the total number of signal bits). The hit value indicates how many signal bits were toggle from a value of 0 to 1 during simulation; the miss value indicates the number of signal bits that were not toggled from a value of 0 to 1 during simulation; and the total value indicates the total number of signal bits within the specified module/instance that Covered was able to simulate.

To the right of this information is the hit, miss and total statistics for signal bits that toggled from a value of 1 to a value of 0.

If the percentage values in the right of the summary table are 100%, this indicates that all signal bits toggled from a value of 0 to 1 and back to 0 during simulating (for the module/instance of this row). If the values of the percentage are less than 100%, this indicates that some signal bits did not fully toggle during simulation and full toggle coverage was not achieved for that module/instance. Note that for a module/instance which does not contain any signals in which Covered was able to simulate, the values of hit, miss, and total will be 0 while the hit percentage value will indicate 100%.

### Verbose Information Description - Both

If the miss value for a particular module/instance was not 0 (indicating that one or more signal bits did not fully toggle during simulation) and the '-d v' option was specified on the command-line (specifying to output verbose reporting information), the signals that were missed during simulation will be output below the summary information per module/instance that contained missed signal bit toggles. In our sample module-based report, there were three signals in module "main" ("go", "state", and "error"), three signals in module "fsma" ("go", "state" and "next_state"), and three signals in module "fsmb" ("go", "next_state" and "state") that were not fully toggled (see lines 53 through 90).

For each signal in the verbose toggle table, the format is the following:

            <signal_name>          0->1: <hexidecimal_value>
            .......................1->0: <hexidecimal_value>

The name of the signal is specified in the upper left corner. The bitwise toggle information for the signal from a value of 0 to a value of 1 is specified in the upper right corner. The hexidecimal value represents bits in the signal, each bit corresponding to the matching bit of the signal. If a bit value is set to the value 1, this indicates that this bit in the signal toggled from a value of 0 to a value of 1. If a bit value is set to the value 0, this indicates that this bit in the signal did NOT toggle from a value of 0 to a value of 1; therefore, full toggle coverage was not achieved for this signal. For example, for the signal called "go" in the module/instance "main", the verbose toggle information looks like:

      go         0->1: 1'b1
      ...........1->0: 1'b0

This is indicating that bit 0 of the signal called "go" successfully toggled from a value of 0 to 1 during simulation (because the bit value at bit location 0 is a value of 1). However, the signal did not toggle from a value of 1 to a value of 0 during simulation, thus the signal was not considered fully toggled.

It is important to note that the hexidecimal values are displayed with the least-significant bit of the signal being output on the far right of the value while the most-significant bit of the signal is output on the far left of the value.

## 14.3. Reading Memory Coverage

### Summary Information Description - Module-based

For module-based reports, the summary table for memory metrics includes information for the name of each module, instantiating one or more memories, that was analyzed and the name of the file in which the module is described in. Lines 93 through 111 of the module-based report show what this information looks like in the report. We have three modules that were scored within our DUT: main, fsma and fsmb. The table shows that all three modules were described in the file "example.v".

### Summary Information Description - Instance-based

For instance-based reports, the summary table for memory metrics includes information for the Verilog hierarchy pertaining to each instance on the left-hand-side of each row. Lines 93 through 111 of the instance-based report show what this information looks like in the report. In our DUT example, there are three instances within the design with the Verilog hierarchies of "main", "main.fsm1" and "main.fsm2".

### Summary Information Description - Both

On the right-hand side of each row in the table are the hit, miss and total numbers for the various memory coverage metrics, followed by a calculated percent of each memory coverage metric that was hit (calculated by taking the number hit during simulation divided by the total number that Covered could have simulated). The hit value indicates how many were executed during the simulation; the miss value indicates the number not executed during simulation; and the total value indicates the total number within the specified module/instance that Covered can simulate. All four metrics (AME toggle 0->1, AME toggle 1->0, AME write and AME read) are listed in the summary section.

If the percentage value in the far left of the summary table is 100%, this indicates that all coverage points that Covered was capable of simulating (for the module/instance of this row) were executed. If the value of the percentage is less than 100%, this indicates that some number of coverage points were not executed and full coverage was not achieved for that module/instance. Note that for a module/instance which does not contain any coverage points in which Covered was able to simulate, the values of hit, miss, and total will be 0 while the hit percentage value will indicate 100%.

### Verbose Information Description - Both

When a module/instance is found to be not fully covered (i.e., the number of each hit coverage points is not equal to the associated number of attainable coverage points), the missed coverage points for each AME in the memory are output to the report as follows:

      <AME>  Written: <0 or 1>  0->1: <hexidecimal_value>
      .....  Read:    <0 or 1>  1->0: <hexidecimal_value> ...

The answers to each of the questions listed above are specified with a 0 (meaning that the answer is "NO") or a 1 (meaning that the answer is "YES"). Note that in the toggle coverage information, like toggle coverage verbose information, the individual bits are grouped together and displayed in hexidecimal form to conserve space and make the task of figuring out exactly which bit positions did not toggle easier. See lines 117 through 151 for an example of this output.

If the -c option is used, Covered outputs the names of the memories that were fully covered during simulation only.

## 14.4. Reading Combinational Logic Coverage

### Summary Information Description - Module-based

For module-based reports, the summary table for combinational logic metrics includes information for the name of each module that was covered and the name of the file in which the module is described in. Lines 154 through 164 of the module-based report show what this information looks like in the report. We have three modules that were scored within our DUT: main, fsma, and fsmb. The table shows that all three modules were described in the file "example.v".

### Summary Information Description - Instance-based

For instance-based reports, the summary table for combinational logic metrics includes information for the Verilog hierarchy pertaining to each instance on the left-hand-side of each row. Lines 154 through 164 of the instance-based report show what this information looks like in the report. In our DUT example, there are three instances within the design with the Verilog hierarchies of "main", "main.fsm1", and "main.fsm2".

### Summary Information Description - Both

On the right-hand side of each row in the table are the hit, miss and total numbers for the combinational logic coverage, followed by a calculated percent of the combinational logic expression values that were hit (calculated by taking the number of combinational logic expression values hit during simulation divided by the total number of expression values that Covered could have simulated). The hit value indicates how many expression values were achieved during the simulation; the miss value indicates the number of expression values not achieved during simulation; and the total value indicates the total number of combinational logic expression values that could have been achieved in the specified module/instance.

If the percentage value in the far left of the summary table is 100%, this indicates that all combinational logic expression values that Covered was capable of achieving (for the module/instance of this row) were hit. If the value of the percentage is less than 100%, this indicates that some number of expression values were not achieved and full coverage was not achieved for that module/instance. Note that for a module/instance which does not contain any combinational logic expressions in which Covered was able to simulate, the values of hit, miss, and total will be 0 while the hit percentage value will indicate 100%.

### Verbose Information Description - Both

The verbose output for combinational coverage is a bit more sophisticated than the line or toggle. Basically, for each expression that was found to not be fully covered (either the expression itself or some sub-expression in the tree was not fully covered), the expression is output with various sub-expressions underlined and identified with a number. Each expression is also supplied with the line number that the expression started at in its module file. In our example, there is an uncovered expression in the module called "main" (see lines 170 through 205 (numbered 5) which contains four uncovered subexpressions (numbered 1 through 4).

Below each expression, there will be one or more tables which specify a particular sub-expression that was not fully covered along with information describing what cases were not covered for that sub-expression.

In the report output above, we see that there was one expression in module "main" that did not achieve 100% coverage that starts on line 14 of the Verilog source. The expression is output to the report with certain sub-expressions underlined and labeled with an integer value for reference.

For this one expression, there were found to be four subexpressions (labeled 1, 2, 3, 4) that were found to not be 100% covered. Taking a look at subexpression 1 report output, the numbers to the right of the string "Expression 1" tell us the number of logical combinations of this subexpression that were hit (in this case 2 combinations were hit) and the total number of logical combinations that this subexpression can have (in this case 3 combinations were achievable). The character string below this information tells us the type of subexpression that we are examining. For subexpression 1, the type is the bitwise AND operator.

The table below this information for subexpression 1, lists the potential combinations that this subexpression could have reached with a '*' character placed underneath the combination(s) that were missed. In the case of subexpression 1, the left and right subexpressions did not evaluate to values of 1 simultaneously. The letter 'L' above each possible combination indicates the value that the left subexpression achieved at the same time as the value under the right subexpression indicated with the letter 'R'. Legal values for a subexpression are '0', '1' or '-' (which indicates that this subexpression value could either be 0 or 1).

## 14.5. Reading FSM Coverage

### Summary Information Description - Module-based

For module-based reports, the summary table for FSM metrics includes information for the name of each module that was covered and the name of the file in which the module is described in. Lines 344 through 354 of the module-based report show what this information looks like in the report. We have three modules that were scored within our DUT: main, fsma and fsmb. The table shows that all three modules were described in the file "example.v".

### Summary Information Description - Instance-based

For instance-based reports, the summary table for FSM metrics includes information for the Verilog hierarchy pertaining to each instance on the left-hand-side of each row. Lines 344 through 354 of the instance-based report show what this information looks like in the report. In our DUT example, there are three instances within the design with the Verilog hierarchies of "main", "main.fsm1" and "main.fsm2".

### Summary Information Description - Both

On the right-hand side of each row in the table are the hit, miss and total numbers for the FSM state coverage, followed by a calculated percent of the FSM states that were hit (calculated by taking the number of FSM states hit during simulation divided by the total number of FSM states that Covered could have simulated). The hit value indicates how many FSM states were executed during the simulation; the miss value indicates the number of FSM states not executed during simulation; and the total value indicates the total number of FSM states within the specified module/instance that Covered can simulate.

To the right of the FSM state summary information is the FSM state-transition hit, miss, total and percentage hit summary information for each module/instance.

If the percentage value in the far left of the summary table is 100%, this indicates that all FSM states and state-transitions that Covered was capable of simulating (for the module/instance of this row) were executed. If the value of the percentage is less than 100%, this indicates that some number of FSM states and/or FSM state-transitions were not executed and full coverage was not achieved for that module/instance. Note that for a module/instance which does not contain any FSMs in which Covered was able to simulate, the values of hit, miss, and total will be 0 while the hit percentage value will indicate 100%.

### Verbose Information Description - Both

The verbose output for FSM coverage is split into the state coverage information and the state transition coverage information. When an FSM is found to be not fully covered (i.e., the number of hit states/state transitions is not equal to the number of attainable states/state transitions), the missed states are output to the report as a list of state values in hexidecimal format as follows:

      <hexidecimal value>

When an FSM is found to be not fully covered, the missed state transitions are output to the report as a list of state transitions in the format below:

      <hexidecimal input state value> -> <hexidecimal output state value>

If the -c option is used or the number of attainable state/state transitions are unknown for the specified FSM, Covered outputs this information in the same way as the missed cases except that the title of the output is "Hit cases". If the number of attainable states/state transitions is unknown, providing the cases that were hit during simulation is useful in aiding the user in determining coverage. In this case, the summary report will output question marks in the missed and total categories, showing the user that this information was not known by Covered.

## 14.6. Reading Assertion Coverage

### Summary Information Description - Module-based

For module-based reports, the summary table for assertion metrics includes information for the name of each module, instantiating one or more assertions, that was covered and the name of the file in which the module is described in. Lines 397 through 405 of the module-based report show what this information looks like in the report. We have three modules that were scored within our DUT: main, fsma and fsmb. The table shows that all three modules were described in the file "example.v".

### Summary Information Description - Instance-based

For instance-based reports, the summary table for assertion metrics includes information for the Verilog hierarchy pertaining to each instance on the left-hand side of each row. Lines 397 through 405 of the instance-based report show what this information looks like in the report. In our DUT example, there are three instances within the design with the Verilog hierarchies of "main", "main.fsm1" and "main.fsm2".

### Summary Information Description - Both

On the right-hand side of each row in the table are the hit, miss and total numbers for the assertion coverage points (ACP), followed by a calculated percent of the ACPs that were hit (calculated by taking the number of ACPs hit during simulation divided by the total number of ACPs that Covered could have simulated). The hit value indicates how many ACPs were executed during the simulation; the miss value indicates the number of ACPs not executed during simulation; and the total value indicates the total number of ACPs within the specified module/instance that Covered can simulate. Note that more than one coverage point may exist within a single assertion coverage module.

If the percentage value in the far left of the summary table is 100%, this indicates that all ACPs that Covered was capable of simulating (for the module/instance of this row) were executed. If the value of the percentage is less than 100%, this indicates that some number of ACPs were not executed and full coverage was not achieved for that module/instance. Note that for a module/instance which does not contain any ACPs in which Covered was able to simulate, the values of hit, miss, and total will be 0 while the hit percentage value will indicate 100%.

### Verbose Information Description - Both

When a module/instance is found to be not fully covered (i.e., the number of hit ACPs is not equal to the number of attainable ACPs), the missed coverage points are output to the report as follows:

      <Instance Name>	<Assertion Name>	<Coverage Point Description>

If the -c option is used, Covered outputs this information in the same way as the missed cases except that the title of the output is "Hit cases" and the number of times each ACP was hit is indicated.

Chapter 13. The exclude Command |  | Chapter 15. Debugging