A USB (Universal Serial Bus) OTG (On-The-Go) controller device and more generally a serial bus control circuit chip are provided which have improved port handler implementations. In one example, different port handler units may be provided which selectively support host and device functionality at the respective ports. In another example, a first port handler for providing host functionality and a second port handler for providing device functionality are provided which are of substantially the same hardware structure. In a further example, at least one port handler is provided that has a low level protocol module for handling packet assembly and/or disassembly, a transfer buffer module for buffering incoming or outgoing data to average out system memory latencies, and a memory access module for generating memory requests in compliance with host and/or device functionality.