M66596 datasheet(97/133 Pages) RENESAS

97 / 133 page

M66596FP/WG

rev .1.00

2006.3.14

page 95 of 127

3.9.4

Setup of data to be transmitted using isochronous transfer in the Peripheral mode.

With isochronous data transmission using this controller at Peripheral mode, after data has been written to the

buffer memory, a data packet can be sent with the next frame in which an SOF packet is detected. This function is

called the isochronous transfer transmission data setup function, and it makes it possible to designate the frame

from which transmission began.

If a double buffer is being used for the buffer memory, transmission will be enabled for only one of the two buffers

even after the writing of data to both buffers has been completed, that buffer memory being the one to which the

data writing was completed first. For this reason, even if multiple IN tokens are received, the only buffer memory

that can be sent is one packet’s worth of data.

When an IN token is received, if the buffer memory is in the transmission enabled state, the controller transmits

the data. If the buffer memory is not in the transmission enabled state, however, a Zero-Length packet is sent and an

underrun error occurs.

Figure 3.26 shows an example of transmission using the isochronous transfer transmission data setup function

with the controller, when “IITV=0 (every frame)” has been set. Sending of a Zero-Length packet is displayed in the

illustration as “Null”, in a shaded box.

Transmission enabled state

Buffer A

Buffer B

Writing completed

Empty state

Buffer A

Buffer B

Null

Data-A

Data-B

Buffer A

Buffer B

Null

Data-A

Data-B

Null

Transmission enabled state

Writing in

progress

Writing completed

Empty state

Null

Empty state

Buffer A

Buffer B

Empty state

Data-A

Received token

Sent packet

Received token

Send packet

Received token

Send packet

SOF packet

Writing in

progress

Empty state

Writing in

progress

Transmission enabled state

Empty state Writing in

progress

Writing completed

Transmission

enabled state

Empty state

Writing in

progress

Writing completed

Empty state

Writing in

progress

Writing completed

Transmission

enabled state

Empty state

Writing in

progress

Writing completed

Transmission

enabled state

Empty state

Writing in

progress

Writing completed

Empty state

Writing in

progress

Writing completed

Transmission

enabled state

Empty state

Figure 3.26 Example of data setup function operation

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