There are two classes of tests are supported by the Root Port Model.
- Sequential tests
- Tests that exist within one process and behave similarly to sequential programs. The test depicted in Test Program: pio_writeReadBack_test0 (later in this chapter) is an example of a sequential test. Sequential tests are very useful when verifying behavior that have events with a known order.
- Parallel tests
- Tests involving more than one process thread. The test sample_smoke_test1 is an example of a parallel test with two process threads. Parallel tests are very useful when verifying that a specific set of events have occurred, however the order of these events are not known.
A typical parallel test uses the form of one command thread and one or more expectation threads. These threads work together to verify the device functionality. The role of the command thread is to create the necessary TLP transactions that cause the device to receive and generate TLPs. The role of the expectation threads is to verify the reception of an expected TLP. The Root Port Model TPI has a complete set of expectation tasks to be used with parallel tests.
Because the example design is a target-only device, only Completion TLPs can be expected by parallel test programs while using the PIO design. However, the full library of expectation tasks can be used for expecting any TLP type when used with the customer design (which can include bus-mastering functionality).