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E5805A USB/RS232 Interface
E5805A USB/RS232 Interface 15
can be connected to a bus- powered hub, which obtains power
from its upstream host and provides up to 100 mA for each
downstream port.
Due to the limited available power for bus- powered hubs,
cascading two bus- powered hubs is an illegal topology, and
devices connected to the second hub will not function. USB
specifications limit the connection of a bus- powered hub to a
self- powered hub or host only.
According to the USB Specification, the maximum limit of hubs
cascaded in series cannot exceed five. In other words, you may
have a maximum of five hubs between any device and the host.
This does not mean that the maximum number of hubs in a
system is five. Indeed, up to seven hubs can be connected
parallel at any given level. You must tally both external and
embedded hubs when counting downstream hubs.
NOTE
The E5805A is a bus-powered device and, therefore, must not be
connected to a bus-powered hub.