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M30245 Group
(1) Related Registers
USB ISO control register
This register controls isochronous transfer of endpoints 1 to 4. This register setting is valid for all the
isochronous transfer IN endpoints that are used simultaneously.
•AUTO_FLUSH bit
This bit controls transmit packet data destruction in isochronous transfer. This bit can be used only
when setting "1" to both ISO_UPDATE bit and ISO bit. The bit is valid only for the IN endpoints 1 to
4 in isochronous transfer.
While ISO_UPDATE bit ="1", AUTO_FLUSH bit ="1", and ISO bit (INxCSR8)="1", the USB function
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control unit, at the time of detecting SOF packet (on receiving from the host PC or on the artificial
SOF operation), automatically 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.
•ISO_UPDATE bit
This bit controls the transmit timing of packet data in isochronous transfer. The bit is valid only for the
IN endpoints 1 to 4 in isochronous transfer.
While ISO_UPDATE bit ="0" and ISO bit ="1", the USB function control unit, at the time of receiving
of an IN token from the host CPU, transmits one packet of the IN FIFO data if SET_IN_BUF_RDY bit
of the corresponding endpoint has been set beforehand to "1".
While ISO_UPDATE bit ="1" and ISO bit ="1", a packet control internal signal is not output to the
transmit control circuit inside the USB function control unit even if SET_IN_BUF_RDY bit of the
corresponding endpoint is set to "1" (even if a data packet whose size is equal to the maximum
packet size is written to the IN FIFO when AUTO_SET function is enabled). Setting "1" to
SET_IN_BUF_RDY bit, which is the packet control signal, is delayed until the next SOF is received
so that transmission of the IN FIFO data packet is delayed. The USB function control unit, on detect-
ing that there are transmit packet data at the time of status updating of the IN FIFO, operates artifi-
cially as having no transmit packet data until the next SOF packet is detected. On detecting SOF
packet, one packet of data which has been set to the IN FIFO is transmitted to the IN token from the
host CPU.
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
page 194 of 354
2. USB function
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