TMP92CZ26A

92CZ26A-436

(d) Isochronous transfer type
Isochronous transfer type is guarant eed transfer by data number that is limited
every each frame.
However, this transfer don’t retry when error occurs. Therefore, Isochronous
transfer type transfer only 2 phases (token, data) and it doesn’t use handshake
phase. And data PID for data phase is DATA0 always because of this transaction
doesn’t support toggle sequence. Therefore, UDC doesn’t confirm when data PID
is receiving mode.
Isochronous transfer type process data every frame. Therefore, all transaction
for finish transfer use receiving SOF token. UDC use FIFO that is divided into
two in Isochronous transfer type.
(d-1) Isochronous transmission mode
Isochronous transfer type form at in transmitt ing is below trans action format.
• Token: IN
• Data: DATA0
Control flow
Isochronous transfer type is frame management. And data that write to
FIFO in endpoint is transmitted by IN token in next frame.
Below are two conditions in FIFO of Isochronous transmission mode
transferring.
X. FIFO for storing data that transmit s to host in present frame
(DATASET reg ister b it = 1)
Y. FIFO for storing data for transmitting host in next frame
(DATASET reg ister b it = 0)
FIFO that is divided into two (packet A and packet B) conditions is whether
X condition or Y condition. Below flow is explained as X Condition (packet A),
Y Condition (packet B) in present frame.
X and Y conditions change one after the oth er by receivin g SOF.
Below is control flow in UDC when receiving IN token.
1. Token packet is received and address endpoint number error is confirmed,
and it checks whether conform applicable endpoint transfer mode with
IN token. If it doesn’t conform, state return to IDLE.
2. Condition of status register is confirmed.
• INVALID condition: State return to IDLE.
3. Data packet is generated.
Data packet is generated. At this point, data PID attach DATA0
always. Next, data is transferre d from FIFO (X condition) of packet A in
UDC to SIE. And it generate DATA packet.
4. CRC bit (counted transfer data of FIFO from first to last) is attached to
last.