Checker Templates

Checker templates are used to include error checking logic into the error simulation. This function/logic effectively catches or masks errors which were not logically masked. For instance, an example could be arithmetic residue checking. The checker is implemented as a function in the verilog simulation. It returns 0 if an error was not caught and 1 if the error was detected. Additionally, for each detected error, the filtered count is incremented so the coverage of the error detection method/unit can be determined.

Built-in Options/Arguments

• inputs: list of inputs

  • name [str]: input name
  • width [int]: input width
  • value [int]: input value
  • datatype [str]: input datatype ("d" for decimal, "h" for hex, and "b" for binary)

• outputs: list of outputs

  • name [str]: output name
  • width [int]: output width

• options [object/dict]: parsed JSON structure from command-line

---

Basic Template

Checker templates use the Mako syntax (similar to Python syntax). A typical checker template will contain:

• Page header
  • Including which arguments are used/required
• Return statement (checker = ...;)
  • Verilog statements
• Other template functionality
  • Possibly additional options/arguments

    <%page args="options, inputs, outputs"/>
        checker = !(
    % for i, m in enumerate(options.mods):
    %   if i == 0:
            ((${options.a} % ${m} + ${options.b} % ${m}) % ${m} == ${options.z} % ${m})
    %   else:
            && ((${options.a} % ${m} + ${options.b} % ${m}) % ${m} == ${options.z} % ${m})
    %   endif
    % endfor
        );

In this case, the command-line options object is being used to specify which inputs/outputs the template operates on (options.a, options.b, and options.z). Additionally, different modulus's are specified in a list (options.mods). Using these parameters/options, a Verilog boolean statement is formed to check the additions of the modulus's against the output. Remember, the template is parsed and run as Verilog!

---

Run

To run such a checker template, a command such as this could be run::

    $ ./inject.py --path $RTL_DIR --lib $CELL_LIBRARY --src add_4bit.v --top Add_syn --num 1 --fault FLIP --input 3 A --input 6 B --output Z --checker adder_mod.mako '{"a": "A", "b": "B", "z": "Z", "mods": [3, 5]}'