Universal Serial Bus (Usb) Controller - HP Vectra VE5 4 Technical Reference Manual

2 System Board
Devices on the PCI Bus

Universal Serial Bus (USB) Controller

The OpenHCI USB controller (USB release 1.0) is implemented as part of
the Bridge chip. It is driven from the PCI bus, and provides support for the
two stacked USB connectors on the back panel. Over-current detection and
protection is provided, but shared between the two ports. The specification
is as follows:
• 12 M bps (bits per second) transfer rate
• Supports up to 127 devices (maximum)
• Isochronous and asynchronous data transfer support
• Up to 5 m per cable segment
• Built in power distribution
• Supports daisy-chaining through a tiered-star, multi-drop topology (up to
6 tiers)
USB works only if the USB interface has been enabled within the HP Setup
program. Currently, only the Microsoft Windows 95 SR 2.1 operating system
provides support for the USB. This operating system is preloaded on the
hard disk of most models of this computer.
28