Cypress EZ-USB FX3 User Manual

EZ-USB FX3 Technical Reference Manual, Document Number: 001-76074 Rev. *F 23
Introduction to EZ-USB FX3
Figure 1-3. USB 2.0 OUT Transaction Versus USB 3.0 OUT Transaction
1.1.3.3 Data Bursting
The SuperSpeed end-to-end protocol supports transmitting the data in bursts (multiple data packets) without receiving an
acknowledgement to improve latency and performance. The protocol allows efficient bus utilization by concurrently
transmitting and receiving over the bus. A transmitter (host or device) can burst multiple packets of data back to back, and the
receiver can transmit data acknowledgements without interrupting the burst of data packets. Also, the host may
simultaneously schedule multiple OUT bursts to be active at the same time as an IN burst. Devices report their ability to
support bursting in their device descriptors. The maximum burst size is 16, and the actual number to be used represents the
number of data packets that can be sent without receiving an acknowledgement.
This bursting approach is explained in Figure 1-3 with an IN endpoint that supports a burst size of four. The host initiates the
burst transfer and indicates the expected sequence number of the first data packet returned (Seq=0) and the number of
packets it wishes to receive (NumP=4). The target device responds with a burst sequence of four data packets without
receiving any handshakes. A fifth data packet cannot be returned until data packet zero is acknowledged and the host has
indicated a request for another data packet (that is, a second ACK packet with NumP=4). In this burst example, the host
continues to request additional data by keeping the NumP value at 4.
Host Controller
High-Speed Device
OUT Token
DATA
ACK
OUT Token
DATA
Host Controller
SuperSpeed Device
ACK Header
DATA Header
+ Payload
1
4
5
6
1
3
2
2
ACK
DATA Header
+ Payload
ACK Header
4
3

Cypress EZ-USB FX3 Specifications

General

Brand	Cypress
Model	EZ-USB FX3
Category	Controller
Language	English