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M30245 Group
(3) Isochronous Transfer: Endpoints 1 to 4 Transmit
Type of Transmit Transfer
When endpoints 1 to 4 IN are used for isochronous transfer, ISO bit and INTPT bit of USB endpoint
x IN control and status register are respectively set to "1" and to "0", for isochronous transfer setting.
Transmit Data Preparation
The endpoint x IN packet data preparation procedure in the isochronous transfer is same as the bulk
transfer.
Refer to " Transmit Data Preparation" of "(2) Bulk Transfer: Endpoints 1 to 4 Transmit" (Continuous
www.DataSheet4U.com
transfer is valid for the bulk transfer only).
Transmit Operation
A packet whose PID is DATA0 is transmitted to the IN token from the host CPU.
When IN token is received from the host CPU while there are no data in IN FIFO, an empty packet
(with 0 data length) is automatically transmitted, an underrun error occurs, and the UNDER_RUN
flag is set to "1".
When the UNDER_RUN flag is set to "1" while the error interrupt is enabled by USB function interrupt
enable register, an error interrupt request occurs (INTST8 is set to "1").
When IN token is received from the host CPU while there are packet data in IN FIFO, data are
transmitted. At this time, the IN FIFO status is updated and the endpoint x IN interrupt request oc-
curs. In isochronous transfer, timing in which data are transmitted to the IN token from the host CPU
differs by setting of ISO_UPDATE bit. When ISO_UPDATE bit is set to "1", setting "1" to
SET_IN_BUF_RDY bit, which is the packet control signal, is delayed until the next SOF packet is
received so that transmission of the IN FIFO data packet is delayed. At this time, whether there are
actual packet data or not, it is replied to the IN token that there are no packet data in the IN FIFO until
the next SOF packet is detected.
Also, for flushing the IN FIFO in isochronous IN transfer by using software, the AUTO FLUSH func-
tion is used.
While ISO_UPDATE bit ="1", AUTO_FLUSH bit ="1", and ISO bit (INxCSR8)="1", the USB function
control unit, at the time of detecting a SOF packet (from the host PC or on the artificial SOF), auto-
matically flushes old data packet inside the IN FIFO if both the IN_BUF_STS1 and the
IN_BUF_STS0 flags are "1" (IN FIFO full state). In isochronous transfer for double buffer, use the
AUTO FLUSH function.
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
page 203 of 354
2. USB function
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