Usb System Architecture - Extron electronics SW USB Series User Manual

•
•
•
•
•
•

USB System Architecture

A USB system architecture refers to the physical bus topology of USB devices connected
to a host device. USB devices include USB hubs, USB peripheral devices, or compound
devices (devices with a combination of USB hubs and USB peripheral devices built into it).
The system is organized in a tiered star topology to prevent multiple or circular attachments
to the bus. Each tier represents a degree of separation from the host device. Per USB
specifications, there are seven supported tiers, starting with the host device (or root hub)
occupying the first tier.
NOTE: Do not connect more than five daisy-chained hubs to the root hub. The
Power supply — An external power supply provides worldwide compatibility.
RS-232 control and pass-through — The SW USB switcher can be controlled by
Simple Instruction Set (SIS) commands received via an RS-232 interface. These SIS
commands can be sent to an RS-232 controllable Extron AV switcher attached to the
SW USB RS-232 Pass Thru port (see
page 27, for an explanation of the available SIS commands).
Contact closure control — Connecting a push-button contact closure device to the
SW USB Contact port or shorting pin 1, 2, 3, or 4 to the ground ( _ ) pin of the Contact
port provides an alternative method of input selection on the SW USB. Commands
issued via contact closure can also be passed through the RS-232 Pass Thru port to
an attached RS-232 controllable Extron switcher (see
Control on page 12 for more information).
Hot key switching — (SW4 USB Plus only) When host emulation is enabled, inputs
can be selected by a combination of key presses on a keyboard connected to port 3 or
4.
Front panel security lockout (executive mode) — To prevent unauthorized access
to the switchers, front panel lock mode can be enabled via front panel controls or SIS
commands to disable all front panel controls.
Port status LEDs — The Active USB LEDs provide visual indication of port status and
activity for USB peripherals and all connected and active host devices.
architecture does not support peripheral devices connected to USB hubs occupying
the seventh tier.
SIS Programming and Control
Setting Up Contact Closure
SW USB Series • Introduction
starting on
2