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15.4.2.2.2 Transaction-Level Operation
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This mode is similar to transfer-level operation with the programmed transfer size equal to one packet
size (either maximum packet size, or a short packet size).
15.4.2.3 Slave Mode
In Slave mode, the application can operate the core either in transaction-level (packet-level) operation
or in pipelined transaction-level operation.
15.4.2.3.1 Transaction-Level Operation
The application handles one data packet at a time per channel/endpoint in transaction-level operations.
Based on the handshake response received on the USB, the application determines whether to retry
the transaction or proceed with the next, until the end of the transfer. The application is interrupted on
completion of every packet. The application performs transaction-level operations for a channel/endpoint
for a transmission (host: OUT/device: IN) or reception (host: IN/device: OUT) as shown in Figure 15.8 (p.
251) and Figure 15.9 (p. 251) .
Host Mode
For an OUT transaction, the application enables the channel and writes the data packet into the
corresponding (Periodic or Non-periodic) transmit FIFO. The core automatically writes the channel
number into the corresponding (Periodic or Non-periodic) Request Queue, along with the last DWORD
write of the packet. For an IN transaction, the application enables the channel and the core automatically
writes the channel number into the corresponding Request queue. The application must wait for the
packet received interrupt, then empty the packet from the receive FIFO.
Device Mode
For an IN transaction, the application enables the endpoint, writes the data packet into the corresponding
transmit FIFO, and waits for the packet completion interrupt from the core. For an OUT transaction, the
application enables the endpoint, waits for the packet received interrupt from the core, then empties the
packet from the receive FIFO.
Note
The application has to finish writing one complete packet before switching to a different
channel/endpoint FIFO. Violating this rule results in an error.
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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