Smart Technologies Smart Board 800 Series - Manual (Page 21)

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.
Root
hub
Hub 1
Hub 2
Hub 3 Hub 4
Hub 5
Hub 7 Hub 6
Function
Host (Tier 1)
Tier 2
Tier 3
Tier 4
Tier 5
Tier 6
Tier 7
Function
Function
Function
Function
Function
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.
A P P E N D I X A
USB 2.0 specification primer
17