Usb Topology - Smart Technologies SMART Board 800 Series User Manual

Extending usb connections

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A P P E N D I X

USB 2.0 specification primer

USB topology

The USB physical network is a tiered star topology. A hub is at the center of each star. Each wire

segment is a point-to-point connection between the host and a hub or function, or a hub connected to

another hub or function. This figure illustrates the topology of a USB network.

Host (Tier 1)

Root

hub

Hub 1

Tier 2

Function

Hub 2

Tier 3

Function

Tier 4

Hub 3

Hub 4

Function

Tier 5

Hub 5

Function

Tier 6

Hub 6

Hub 7

Tier 7

Function

Timing constraints for hub and cable propagation times allow a maximum of seven tiers, including the

root tier. In seven tiers, a maximum of five non-root hubs can be supported in a communication path

between the host and any device. Note that a compound device occupies two tiers; therefore, it

cannot be attached at tier seven where only functions can be used.

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Smart board 800i series