Toshiba TLCS-900/H1 Series Manual page 247

3.10.6 Transfer mode and Protocol Transaction
The UDC performs the following automatically in hardware;
• Receive packet
•
Determine address endpoint transfer mode
• Error process
•
Confirm toggle bit CRC of data receiving packet
• Generate toggle bit CRC of data transmitting packet, etc
•
Handshake answer
(1) Protocol outline
Format of USB packet is shown below. This is processed during transmission and
receiving by hardware into the UDC.
• SYNC field
This field always comes first in each packet, and input data and internal CLK is
synchronized in the UDC.
• Packet identification field (PID)
This field follows SYNC field in every USB packet. The UDC distinguishes the
PID type and determines the transfer type by decoding this code.
•
Address field
The UDC uses this field to confirm whether or not this function was specified by
the host. The UDC compares the address with that set to the ADDRESS register. If
the address accords with it, the UDC continues the process. If the address does not
accord, the UDC ignores this token.
•
Endpoint field
If sub-channels of more than two are needed in fields of 4 bits, it decides the
function. The UDC can support a maximum of seven endpoints, excluding the
control endpoint. Tokens for endpoints that are not permitted are ignored.
• Frame number field
A field of 11 bits is added by the host at each frame. This field follows the SOF
token that is transmitted first in each frame, and the frame number is specified.
The UDC reads the content of this field when the SOF token is received, and sets
the frame number to the FRAME register.
• Data field
This field is data of unit byte in bytes 0 to 1023. When receiving it, the UDC
transfers only part of this data to FIFO, and after CRC is confirmed, an interrupt
signal is asserted and the UDC informs FIFO that data transfer is completed.
When transmitting, following IN token, FIFO data is transferred. Finally, data
CRC field is attached.
• CRC function
5 bits CRC is attached to the token, and 15 bits CRC to the data. The UDC
automatically compares the CRC of the received data with the attached CRC.
When transmitting, CRC is generated automatically and is transmitted. This
function may be compared by various transfer modes.
92CH21-245
TMP92CH21
2009-06-19