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TMP92CZ26A
92CZ26A-420
3.16.6 Transfer mode and Protocol Transaction
UDC perform automatically in hardware as follows;
• Receive packet
• Judge address endpoint transfer mode
• Error process
• Confirm toggle bit CRC of data receiving packet
• Generate including toggle bit CRC of data transmitting packet
• Handshake answer
(1) Protocol outline
Format of USB packet is showed to below. This is processed during transmission and
receiving by hardware into UDC.
• SYNC field
This field always exists first of each packet, and input data and internal CLK is
synchronized in UDC.
• Packet identification field (PID)
This field follows on SYNC field at every USB packet. UDC judge PID type and
judge transfer type by decoding this cord.
• Address field
UDC confirms whether this function was appointed or not from host by using
this field. UDC compares with address that was set to ADDRESS register. If an
address accords with it, UDC continues process. If an address doesn’t accord, UDC
ignores this token.
• Endpoint field
If sub-channels more than two is needed in field of 4 bits, it decides it function.
UDC can be supported endpoint except for control endpoint (max 7 endpoint).
Token for endpoint that is permitted is ignored.
• Frame number field
Field of 11 bits is added +1 at every frame by host. This field follows to SOF token
that is transmitted in first of each frame, and frame number is appointed. UDC
reads content of this field when SOF token is received, and it sets frame number to
FRAME register.
• Data field
This field is data of unit byte in 0 to 1023 bytes. When receiving it, UDC
transfers only part of this data to FIFO, after CRC was confirmed, interrupt signal
is asserted. And UDC informs finishing transferring data to FIFO. When
transmitting, following IN token, data of FIFO is transferred. Finally, data CRC
field is attached.
• CRC function
Token is attached 5 bits, data is attached CRC of 15 bits. UDC compares CRC of
received data with attached CRC automatically. When transmission, CRC is
generated automatically and it is transmitted. This function may be compared by
various transfer modes.