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iX-1-11
IX
USB
outtransaction
In OUT transactions, data reception is started regardless of the available space in the FIFO. Thus, this product
provides satisfactory throughput by assigning a FIFO region about twice as large as the maximum packet size
since it can read the FIFO data via the Port interface, for example, and receive data while creating an available
space concurrently.
After all data are successfully received in an OUT transaction, the transaction is closed and an ACK
response is returned. In addition, the firmware receives an OUT_TranACK status of the relevant endpoint
(EPx{x=0,a,b,c,d}IntStat.OUT_TranACK bit). Furthermore, the FIFO is updated to acknowledge the data
reception and to secure a space for the data.
In OUT transactions on the EPa, EPb, EPc, and EPd endpoints, reception of all short-packet data causes an
OUT_ShortACK status (EPx{x=a,b,c,d}IntStat.OUT_ShortACK bit) to be issued, in addition to executing the
above closing process. If the EPx{x=a,b,c,d}Control.DisAF_NAK_Short bit is cleared, the relevant endpoint's
EPx{x=a,b,c,d}ForceNAK bit is set.
If a toggle miss-match has occurred in an OUT transaction, an ACK response is returned to the transaction but
no status is issued. Accordingly, the FIFO is not updated.
In the event of an error in an OUT transaction, no response is returned to the transaction. And an OUT_TranErr
status (EPx{x=0,a,b,c,d}IntStat.OUT_TranErr bit) is issued. Accordingly, the FIFO is not updated.
If not all data are received in an OUT transaction, a NAK response is returned to the transaction and the
OUT_TranNAK status (EPx{x=a,b,c,d}IntStat.OUT_TranNAK bit) is issued. Accordingly, the FIFO is not
updated.
Figure IX.1.4.1.2 illustrates how a successful OUT transaction is executed and closed.
(a) The host issues an OUT token addressed to an OUT endpoint present on this node.
(b) Next, the host sends a data packet under the maximum packet size. The macro writes these data in the
relevant endpoint's FIFO.
(c) Upon data reception, the macro automatically returns an ACK response. In addition, it sets registers to be
automatically set up and issues a status to the firmware.
OUT
a
ACK
c
DATA
b
HosttoDevice
DevicetoHost
FigureIX.1.4.1.2OUTTransaction