Single Transaction Translator(STT) and Multiple Transaction Translator (MTT)
Question: what is the difference between Single Transaction Translator(STT) and Multiple Transaction Translator (MTT)
A USB hub has two choices for organizing Transaction Translators (TTs). A hub can have one TT for all downstream facing ports that have full-/low-speed devices attached ( called Single Transaction Translator---STT) or the hub can have one TT for each downstream facing port ( called Multiple Transaction Translator---MTT) . For Multiple Transaction Translator (MTT) , each downstream port of the Hub has its own transaction translator to provide the best USB performance no matter what class of USB device is connected it. When implementing a USB Hub system, consider the types of devices and the speeds they will run at. If downstream USB devices are either all high-speed or just a single full-/low-speed device a lower cost, a Single Transaction Translator (STT) hub can be considered. If the application is multiple full-/low-speed devices with a need for bandwidth, a Multiple Transaction Translator (MTT) hub should be used. In the case of consumers connecting full-/low- speed devices with USB 2.0 hubs that use Single Transaction Translator (STT) technology, they are bound to face performance issues when multiple USB devices are used.