One of the most common form of sequence driver use models is the scenario where the sequencer sends request sequence_items to the driver which executes the request phase of the pin level protocol, and then the driver responds to the response phase of the pin-level transaction returning the response back to the sequence. In this use model the flow of data is bidirectional and a new request phase cannot be started until the response phase has completed. An example of this kind of protocol would be a simple peripheral bus such as the AMBA APB.
