IN
Only a!er swrdy=0 can you fill in data to e0#w;
Se$ng a crsr a!er the data is filled will make the
handshake phase reply ACK;
DATA
ACK
OUT
DATA
ACK
EP0
EP0
host -> device
host -> device
host -> device
device -> host
device -> host
host -> device
IN
DATA
ACK
OUT
DATA
ACK
EP1 – EP7
EP1 – EP7
host -> device
host -> device host -> device
device -> host host -> device
device -> host
A!er the crsr is set to 1, the data sent from the host can enter e0rfr,
and the handshake phase will reply ACK, otherwise the data will be
blocked out of e0rfr, and the handshake phase will reply NAK.
Only a!er exrs=0 can you fill in data to ex#w;
A!er the data is filled in, se$ng an exr will make the
handshake phase reply ACK;(X=1...7)
A!er exr is set to 1, the data sent by the host can enter exrfr and
reply ACK in the handshake phase, otherwise the data will be
blocked out of exrfr, and the handshake phase will reply NAK.
(X=1...7)
Fig. 18.2: USB communication method
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