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TMP92CZ26A
92CZ26A-432
(c-4) Stage management
UDC manages each stage of control transfer by hardware.
Each stage is changed by receiving token from USB host, or CPU accesses
register. Each stage in control transfer type has to process combination software.
UDC detect following contents from 8-byte data in SETUP stage. (It contents is
showed to following.) And, stage is managed by judging control transfer type.
• There is data stage or not
• Data stage direction
Control read transfer type is jugged control write transfer type, control write
transfer type (No data stage) by them.
Below are various conditions for changing stage in control transfer.
If receiving token for next stage from host before switching next stage from
state of internal UDC, NAK handshake is returned and BUSY is informed to USB
host. In all control transfer type, if SETUP token is received from host always,
present transaction is stopped, and it switches SETUP stage in UDC. CPU receive
new INT_SETUP even if it is processing previous control transfer.