Test Coverage meanings

The meaning of Test Coverage results

The test coverage analysis gathers its statistics about testing from three sources:

• Connection test - XJTAG automatically calculates the test coverage of the built-in connection test.
• Non-JTAG device tests - busses in Test Device files can have test coverage specified for them, which describes which faults are checked for by the tests in the device file.
• Extra information - functional test coverage can be manually specified for groups of nets. This can be used to:
  • Mark nets/devices that are inherently tested - e.g. power supply components.
  • Mark untested devices/nets that the designer knows about - e.g. analogue signals.
  • Mark nets/devices that could be tested, but which don't have any tests written yet.

Pins can have various classifications:

• Power Pin: This pin is part of a power/ground net and XJTAG cannot exercise it.

  N.B. Power pins also include pins on termination reference voltage nets.

• JTAG Pin: This pin is part of the JTAG chain. Therefore, if JTAG works correctly on the circuit board, this pin can be assumed tested.
• Tested for Open Circuit Errors: Tests would detect if this pin were open-circuit.
• Tested for Short Circuit Errors: Tests would detect if this pin were short-circuited to another pin or net.
• Tested for Stuck Low/High Errors: Tests would detect if this pin were shorted to Ground or to a Power net.
• Functionally Tested: The pin has been marked as functionally tested, either in the Functional Tests tab or in the test coverage of a device file (see Test Device Files Screen).
• Untested: XJDeveloper is unable to deduce any test coverage on this pin.

Apart from Untested, Power and JTAG, multiple classifications can apply to one pin. A pin counts toward the Tested Pins total if it is not either a Power pin or an Untested pin.

Untestable pins

Some circuit design programs generate netlists which create a net even for unconnected pins on a device. If the device with these unconnected pins is not a JTAG device, such pins are inherently untestable. XJDeveloper excludes these pins from all the test coverage totals, but indicates the number of excluded pins next to the total number of pins for the appropriate device/net at a circuit and board level.