Texas Instruments OMAP5912 Reference Manual page 1471

Non-Isochronous OUT (USB HOST −> MPU) DMA Transactions
End of Transfer Interrupt (IRQ_SRC.RXn_EOT)
Transaction Count Interrupt (IRQ_SRC.RXn_CNT)
SPRU761A
The USB device controller transmit DMA channels 0 through 2 are connected
to OMAP5912 DMA controller requests DMA_REQ_26, DMA_REQ_27, and
DMA_REQ_29, respectively.
During non-ISO transfers to a DMA operated OUT endpoint, a request to the
MPU DMA controller is generated when data have been placed into endpoint
FIFO and must be read. ACK and NAK interrupts are always disabled
automatically by the core for DMA operated endpoints.
There are two dedicated maskable interrupts per DMA channel to control
non-ISO OUT transfers.
This interrupt signals that the core has detected an end-of-transfer (EOT).
EOT occurs in the two following cases:
-
When the last valid transaction to the endpoint is either an empty packet
(ACK and buffer empty) or a packet whose size is less than the physical
endpoint buffer size (ACK and buffer not full)
-
When the number of received transactions has reached the programmed
value in the RXDMAn.RXn_TC field, if the RXDMAn.RXn_STOP bit has
been set by the MPU
After an end of transfer interrupt, the MPU must set CTRL.SET_FIFO_EN for
the endpoint to reenable the channel.
The MPU must not initiate a new RX DMA transfer until it receives an
end-of-transfer interrupt.
The intent of this interrupt is watermark control. It can be used by the MPU to
monitor the file size of incoming transfers and take appropriate actions if, for
instance, the file being received exceeds an expected size.
A transaction count interrupt does not disable the ongoing DMA transfer.
A transaction count interrupt occurs each time the number of received
transactions (and not bytes) has reached the programmed value in the receive
transaction counter for the DMA channel. One transaction has a size equal to
the buffer size of the selected non-ISO endpoint. RXn_COUNT interrupt is
USB Device Controller
Universal Serial Bus (USB) 179