Christian Légaré
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Re: Nov 28 - Day 3: Understanding the USB Protocol
Christian Légaré   11/28/2012 2:45:30 PM
When an application sends N bytes how does the peer know when the entire application packet has been received?

Good question!

As you saw from the packets, there are not "length of transfer" So, USB uses what is called a Zero Length Packet «)ZLP). If a packet received is smaller than the Maximium packet size for the transfer  mode at a certain speed, than it knows that is was the last packet. Otherwise, the transmitter has to send a ZLP to signel the end of the transfer.


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