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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262--, Revision: 004US
287
USB 1.1 Device Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network
Processors
To assemble control transfers, the host sends a control transaction to tell the UDC what
type of control transfer is taking place (control read or control write), followed by one
or more data transactions. The setup is the first stage of the control transfer. The
device must respond with an ACK or no handshake (if the data is corrupted).
The control transaction, by default, uses a DATA0 transfer and each subsequent data
transaction toggles between DATA1 and DATA0 transfers. A control write to an endpoint
uses OUT transactions.
Control reads use IN transactions. The transfer direction is the opposite of the last data
transaction. The transfer direction is used to report status and functions as a
handshake.
For a control write, the last transaction is an IN from the UDC to the host. For a control
read, the last transaction is an OUT from the host to the UDC. The last data transaction
always uses a DATA1 transfer, even if the previous transaction used DATA1.
8.3.5.4
Interrupt Transaction Type
The host uses interrupt transactions to query the status of the device. Like bulk
transactions, interrupt transactions begin with a setup packet, followed by an optional
data packet, then a handshake packet. Interrupt transactions, by default, use DATA0
type transfers.
shows the four types of interrupt transactions.
8.3.6
UDC Device Requests
The UDC uses its control, status, and data registers to control and monitor the transmit
and receive FIFOs for endpoints 1 - 15. The host controls all other UDC configuration
and status reporting using device requests that are sent as control transactions to
endpoint 0 via the USB.
Each setup packet to Endpoint 0 is 8 bytes long and specifies:
• Data transfer direction: host to device, device to host
• Data transfer type:
— Standard
— Class
— Vendor
• Data recipient:
— Device
— Interface
— Endpoint
— Other
Table 117.
Interrupt Transaction Formats
Action
Token Packet
Data Packet
Handshake Packet
Host successfully received data from UDC
IN
DATA0
ACK
UDC temporarily unable to transmit data
IN
None
NAK
UDC endpoint needs host intervention
IN
None
STALL
Host detected PID, CRC, or bit stuff error
IN
DATA0
None
†
Packets from UDC to host are boldfaced.