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Intel
®
IXP42X product line and IXC1100 control plane processors—Universal Serial Bus (USB)
v1.1 Device Controller
Intel
®
IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor
DM September 2006
476 Order Number: 252480-006US
18.3.5.2 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 Table 168.
18.3.5.3 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.
Table 169 shows the four types of control transactions.
Table 167. 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 168. 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 169. 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.