Datasheet
SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
884
37.6.18 UDPHS DMA Channel Control Register
Name: UDPHS_DMACONTROLx [x = 1..5]
Address: 0xFFF78328 [1], 0xFFF78338 [2], 0xFFF78348 [3], 0xFFF78358 [4], 0xFFF78368 [5]
Access: Read/Write
• CHANN_ENB (Channel Enable Command)
0: DMA channel is disabled at and no transfer will occur upon request. This bit is also cleared by hardware when the chan-
nel source bus is disabled at end of buffer.
If the UDPHS_DMACONTROL register LDNXT_DSC bit has been cleared by descriptor loading, the firmware will have to
set the corresponding CHANN_ENB bit to start the described transfer, if needed.
If the UDPHS_DMACONTROL register LDNXT_DSC bit is cleared, the channel is frozen and the channel registers may
then be read and/or written reliably as soon as both UDPHS_DMASTATUS register CHANN_ENB and CHANN_ACT flags
read as 0.
If a channel request is currently serviced when this bit is cleared, the DMA FIFO buffer is drained until it is empty, then the
UDPHS_DMASTATUS register CHANN_ENB bit is cleared.
If the LDNXT_DSC bit is set at or after this bit clearing, then the currently loaded descriptor is skipped (no data transfer
occurs) and the next descriptor is immediately loaded.
1: UDPHS_DMASTATUS register CHANN_ENB bit will be set, thus enabling DMA channel data transfer. Then any pend-
ing request will start the transfer. This may be used to start or resume any requested transfer.
• LDNXT_DSC: Load Next Channel Transfer Descriptor Enable (Command)
0: No channel register is loaded after the end of the channel transfer.
1: The channel controller loads the next descriptor after the end of the current transfer, i.e. when the
UDPHS_DMASTATUS/CHANN_ENB bit is reset.
If the UDPHS_DMA CONTROL/CHANN_ENB bit is cleared, the next descriptor is immediately loaded upon transfer
request.
DMA Channel Control Command Summary
31 30 29 28 27 26 25 24
BUFF_LENGTH
23 22 21 20 19 18 17 16
BUFF_LENGTH
15 14 13 12 11 10 9 8
––––––––
76543210
BURST_LCK DESC_LD_IT END_BUFFIT END_TR_IT END_B_EN END_TR_EN LDNXT_DSC CHANN_ENB
LDNXT_DSC CHANN_ENB Description
0 0 Stop now
0 1 Run and stop at end of buffer
1 0 Load next descriptor now
1 1 Run and link at end of buffer