Sign in with
Sign up | Sign in

Single TT Or Multi TT

USB Technology: Multi-TT Hub Goes Head-to-Head With Single-TT

One way to solve the problem is to increase your total bandwidth by plugging the USB 1.1 devices into a USB 2.0 hub.

All USB 2.0 hubs have at least one built-in transaction translator (TT) so that they can be downwards compatible. The TT automatically recognizes which USB category is connected on a particular port and translates any USB 1.1 signals to USB 2.0. There is a catch: you only have one TT for all your available ports, which keeps the bandwidth to the system down to no more than 12 mbit/s.

Overall performance suffers whenever all the devices on the hub have to share one transaction translator.

You can get around this problem by using higher-quality USB hubs that have as many TTs as they do ports. No longer do the devices on the hub have to wait their turn for some free bandwidth; the TTs optimally embed all the separate data streams in the USB 2.0 data stream.

Each port in this hub has its own transaction translator. Only three are in use, though: a USB 2.0 device is connected to the fourth port, and its data doesn't need to be translated before being transferred.
React To This Article