Datasheet

993
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
40.6.1.3 USB Transfer Event Definitions
As indicated below, transfers are sequential events carried out on the USB bus.
Notes: 1. Control transfer must use endpoints with no ping-pong attributes.
2. Isochronous transfers must use endpoints with ping-pong attributes.
3. Control transfers can be aborted using a stall handshake.
A status transaction is a special type of host-to-device transaction used only in a control transfer. The control transfer
must be performed using endpoints with no ping-pong attributes. According to the control sequence (read or write), the
USB device sends or receives a status transaction.
Figure 40-4. Control Read and Write Sequences
Notes: 1. During the Status IN stage, the host waits for a zero length packet (Data IN transaction with no data) from the device
using DATA1 PID. Refer to Chapter 8 of the Universal Serial Bus Specification, Rev. 2.0, for more information on the
protocol layer.
Table 40-5. USB Transfer Events
Transfer
TransactionDirection Type
CONTROL (bidirectional) Control
(1)(3)
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)
Interrupt IN
Data IN transaction → Data IN transactionIsochronous IN
(2)
Bulk IN
OUT (host toward device)
Interrupt OUT
Data OUT transaction → Data OUT transactionIsochronous OUT
(2)
Bulk OUT
Control Read
Setup TX Data OUT TX Data OUT TX
Data Stage
Control Write
Setup Stage
Setup Stage
Setup TX
Setup TX
No Data
Control
Data IN TX Data IN TX
Status Stage
Status Stage
Status IN TX
Status OUT TX
Status IN TX
Data Stage
Setup Stage Status Stage