In reply to dhserfer:
I’m not sure what you mean with ‘complex driver’. But the driver has to implement the pin behavior of its pinlevel interface, i.e. bus/interface protocol. It takes a sequence item and provides the data to this interface. Optional it might generate a rsp and give this baack to the sequnence. Sequnces define how the sequence items will be generated. A sequence mighht consist of other sequences, like reset or a config sequence. In special cases you might even implement checker functionality. Because the sequence is on the transaction level it is easy to handle. It does not know anything about clock and timimg. The only scheme is the order of the execution of sub-sequences or sequence items.