I was reading the datasheet for a USB switch chip recently:
This chip supports both USB 3.0 (with its twisted pair unidirectional signals TX+/- and RX+/-) and USB 2.0 (with bidirectional D+/-). This particular example is a 2-to-1 chip: one device, two hosts, or two devices, one host.
What puzzled me is it has a mode where the Superspeed TX/RX pins and High Speed D pins can go to a different place. Eg for a single device, Superspeed pins go to host A and High Speed pins to host B.
Does this make any sense? Is there an application you might use to route that? I can imagine a niche where you only want to connect the High Speed pins (because firmware or whatever is broken for 3.0), but they don't have an 'off' mode, only an A/B select.
Is SuperSpeed alone likely to work? And how is a device likely to fare if there are two different hosts talking to its SS and HS pins?
It sounds like a bit of a strange feature, and I'm wondering why they included it.
Theo