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SPRU761A
register. However, if needed by the application, the MPU can unselect the
endpoint number in the TX/RXDMA_CFG register during a DMA transfer. The
resulting behavior is:
-
For RX transfer:
J
If RX DMA request is active for the endpoint when the endpoint is
unselected, deconfiguration is effective only at the end of the RX DMA
request (that is, after all the DMA data have been read). When
double-buffering is used, the deconfiguration is effective after both
buffers have been read (if both buffers were not empty at unselection).
An EOT interrupt is asserted if an end-of-transfer is detected.
J
If the RX DMA request is not active when unselection occurs, the
effect is immediate.
-
For TX transfer:
J
If the request is active when the endpoint is unselected,
deconfiguration is effective after the TX DMA request has been
handled and the TX data have been sent through an IN transaction
(both buffers in case of double-buffering with both buffers full). No
TX_DONE interrupt is asserted even if TXDMAn.TSC bit value is 0
after the transaction.
J
If the TX DMA request is inactive when the endpoint is unselected,
deconfiguration is effective when all data available in TX buffer(s)
have been sent through IN transaction(s). If the TXDMAn_TSC value
is 0 at this point, no TX_DONE interrupt is asserted. If TX_DONE
interrupt had already been asserted when the endpoint is deselected,
configuration is effective only after the TX_DONE interrupt handling.
TX/RXDMA_CFG.TX/RXDMAn_EP reflects the endpoint value until
deconfiguration is effective. The MPU must read this register to know if the
channel has been disabled yet or not. It must wait until the read value is 0
before performing other actions to the endpoint. After effective
deconfiguration, all transactions to the endpoint generate an endpoint-specific
interrupt (if non-transparent).
If the selected endpoint is of isochronous type, deconfiguration is effective
after the TX/RX request has been serviced, and the subsequent isochronous
transactions are handled at SOF interrupt through the endpoint registers
(EP_NUM and STAT_FLG).
USB Device Controller
Universal Serial Bus (USB)
191
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