S2R72V27 Datasheet, PDF (16/41 Pages) Epson Company – Supports HS (480 Mbps), FS (12 Mbps), and LS (1.5 Mbps) transfer

4. Explanation of Functions
CPU
FIFO
Channel
USB Device
Read
Write
FIFO_Empty
Free _{quantity >=}
MaxPktSize
IN token
NAK ^handshake
IN token
IN transaction
(NAK response)
FIFO_Full
Read
Transfer ^received
DATA ^packet
ACK _handshake
Free _{quantity <}
MaxPktSize
IN transaction
(Data reply)
FIFO_Empty
Empty
Data
Free _{quantity >=}
MaxPktSize
IN token
NAK ^handshake
IN transaction
(NAK response)
Fig. 4.6 Typical data flow (with FIFO assigned for MaxPktSize and IN transfer)
CPU
FIFO
Channel
Write
Read
FIFO_Empty
Write
Data _{quantity <}
MaxPktSize
USB Device
FIFO_Full
FIFO_Empty
Write
FIFO_Full
Empty
Data
Data _{quantity >=}
MaxPktSize
Transfer ^sent
Data _{quantity <}
MaxPktSize
Data _{quantity >=}
MaxPktSize
Transfer ^sent
OUT _token
DATA _packet
ACK ^handshake
OUT _token
DATA _packet
ACK ^handshake
OUT transaction
OUT transaction
Fig. 4.7 Typical data flow (with FIFO assigned for MaxPktSize and OUT transfer)
S2R72V27 Data Sheet (Rev. 1.00)
EPSON
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