Toshiba TLCS-900/H1 Series Manual page 263

(d) Isochronous transfer type
Isochronous transfer type is guaranteed transfer by data number that is limited
to each frame.
However, this transfer does not retry when an error occurs. Therefore,
Isochronous transfer type transfer only 2 phases (token, data) and it does not use
handshake phase. And data PID for data phase is always DATA0 because this
transaction does not support toggle sequence. Therefore, UDC does not confirm
when data PID is in receiving mode.
Isochronous transfer type processes data every frame. Therefore, all
transactions for completed transfers use receiving SOF token. The UDC uses
FIFO that is divided into two in Isochronous transfer type.
(d-1) Isochronous transmission mode
The transaction format for Isochronous transfer type format in transmitting
is given below.
•
Token: IN
• Data: DATA0
Control flow
Isochronous transfer type is frame management. And data that is written to
FIFO in endpoint is transmitted by IN token in the next frame.
Below are two conditions in FIFO of Isochronous transmission mode
transferring.
X. FIFO for storing data that transmits to host in present frame
(DATASET register bit = 1)
Y. FIFO for storing data for transmitting host in next frame
(DATASET register bit = 0)
FIFO that is divided into two (packet A and packet B) conditions is whether
X condition or Y condition. The flow below is explained as X Condition (packet
A), Y Condition (packet B) in present frame.
X and Y conditions change one after the other by receiving SOF.
Control flow in the UDC when receiving IN token is shown below.
1. Token packet is received and address endpoint number error is confirmed,
and it checks whether the relevant endpoint transfer mode corresponds
with the IN token. If it does not correspond, the state returns to IDLE.
2. Condition of status register is confirmed.
• INVALID condition: State returns to IDLE.
3. Data packet is generated.
Data packet is generated. At this point, data PID is always attached to
DATA0. Next, data is transferred from FIFO (X condition) of packet A in
UDC to SIE, and DATA packet is generated.
4. CRC bit (counted transfer data of FIFO from first to last) is attached to
last.
92CH21-261
TMP92CH21
2009-06-19