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TMP92CZ26A
92CZ26A-436
(d) Isochronous transfer type
Isochronous transfer type is guaranteed 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 format in transmitting is below transaction 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 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. Below flow 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.
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 transferred 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.