Specifications

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USB Transfers—Closer Look at an Isochronous Transfer
 Isochronous transfer
 Contains IN/OUT and DATA transactions
 Fixed transfer rate with a defined number of bytes transferred
 Transferred in bursts
 Host guarantees time scheduled transfers per frame
 Insures data can get through on a busy bus even if the data does not
need to transmit at real time
 Good for constant rate applications such as audio
IN
PID=1101
DATA0
PID=0011
Host sends IN packet and the device responds with the
data requested. No error checking.
OUT
PID=0001
DATA0
PID=0011
Host sends OUT packet and then sends the data. No
error checking.
Host → Device
Device → Host
This is the Isochronous transfer and as we mentioned earlier there is no handshake
packets associated with this transfer type.