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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—USB 1.1 Device
Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
286
Order Number: 306262-004US
8.3.5.2
Isochronous Transaction Type
Isochronous transactions ensure constant-rate, error-tolerant transmission of data
between the host and UDC. The host schedules isochronous packets during every
frame.
The USB protocol allows isochronous transfers to take up to 90% of the USB
bandwidth. Unlike bulk transactions, if corrupted data is received, the UDC will continue
to process the corrupted data that corresponds to the current start of frame indicator.
Isochronous transactions do not support a handshake phase or retry capability. Two
packet types are used to construct isochronous transactions: token and data. The types
of isochronous transactions based on data direction are shown in
.
8.3.5.3
Control Transaction Type
The host uses control transactions to configure endpoints and query their status. Like
bulk transactions, control transactions begin with a setup packet, followed by an
optional data packet, then a handshake packet. Control transactions, by default, use
DATA0 type transfers.
shows the four types of control transactions.
Table 114.
Bulk Transaction Formats
Action
Token Packet
Data Packet
Handshake Packet
Host successfully received data from UDC
IN
DATA0/DATA1
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/DATA1
None
UDC successfully received data from host
OUT
DATA0/DATA1
ACK
UDC temporarily unable to receive data
OUT
DATA0/DATA1
NAK
UDC endpoint needs host intervention
OUT
DATA0/DATA1
STALL
UDC detected PID, CRC, or bit stuff error
OUT
DATA0/DATA1
None
†
Packets from UDC to host are boldfaced.
Table 115.
Isochronous Transaction Formats
Action
Token Packet
Data Packet
Host received data from UDC
IN
DATA0
UDC received data from host
OUT
DATA0
†
Packets from UDC to host are boldfaced.
Table 116.
Control Transaction Formats
Action
Token Packet
Data Packet
Handshake Packet
UDC successfully received control from host
SETUP
DATA0
ACK
UDC temporarily unable to receive data
SETUP
DATA0
NAK
UDC endpoint needs host intervention
SETUP
DATA0
STALL
UDC detected PID, CRC, or bit stuff error
SETUP
DATA0
None
†
Packets from UDC to host are boldfaced.