Manual

850
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
44.4.3 USB Transfer Event Definitions
A transfer is composed of one or several transactions;
Notes: 1. Control transfer must use endpoints with one bank and can be aborted using a stall handshake.
2. Isochronous transfers must use endpoints configured with two or three banks.
An endpoint handles all transactions related to the type of transfer for which it has been
configured.
44.4.4 USB V2.0 High Speed BUS Transactions
Each transfer results in one or more transactions over the USB bus.
There are five kinds of transactions flowing across the bus in packets:
1. Setup Transaction
2. Data IN Transaction
3. Data OUT Transaction
4. Status IN Transaction
5. Status OUT Transaction
Table 44-2. USB Communication Flow
Transfer Direction Bandwidth Endpoint Size Error Detection Retrying
Control Bidirectional Not guaranteed 8,16,32,64 Yes Automatic
Isochronous Unidirectional Guaranteed 8-1024 Yes No
Interrupt Unidirectional Not guaranteed 8-1024 Yes Yes
Bulk Unidirectional Not guaranteed 8-512 Yes Yes
Table 44-3. USB Transfer Events
CONTROL
(bidirectional)
Control Transfers
(1)
• Setup transaction → Data IN transactions →Status OUT transaction
• Setup transaction → Data OUT transactions →Status IN transaction
• Setup transaction → Status IN transaction
IN
(device toward host)
Bulk IN Transfer • Data IN transaction → Data IN transaction
Interrupt IN Transfer • Data IN transaction → Data IN transaction
Isochronous IN Transfer
(2)
• Data IN transaction → Data IN transaction
OUT
(host toward device)
Bulk OUT Transfer • Data OUT transaction → Data OUT transaction
Interrupt OUT Transfer • Data OUT transaction → Data OUT transaction
Isochronous OUT Transfer
(2)
• Data OUT transaction → Data OUT transaction