Atmel Evaluation Kit AT91SAM9G25-EK AT91SAM9G25-EK Data Sheet

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SAM9G25 [DATASHEET]

11032C–ATARM–25-Jan-13

0 = Cleared automatically when read by software.

1 = Set by hardware when a descriptor has been loaded from the system bus.

Valid until the CHANN_ENB flag is cleared at the end of the next buffer transfer.

This field determines the current number of bytes still to be transferred for this buffer.

This field is decremented from the AHB source bus access byte width at the end of this bus address phase.

The access byte width is 4 by default, or less, at DMA start or end, if the start or end address is not aligned on a word boundary.

At the end of buffer, the DMA accesses the UDPHS device only for the number of bytes needed to complete it.

This field value is reliable (stable) only if the channel has been stopped or frozen (UDPHS_EPTCTLx register NT_DIS_DMA bit is 
used to disable the channel request) and the channel is no longer active CHANN_ACT flag is 0.

Note:

For OUT endpoints, if the receive buffer byte length (BUFF_LENGTH) has been defaulted to zero because the USB 
transfer length is unknown, the actual buffer byte length received will be 0x10000-BUFF_COUNT.