Datasheet

39.6.30 Device DMA Channel x Status Register
Name: USBHS_DEVDMASTATUSx
Offset: 0x030C + (x-1)*0x10 [x=1..7]
Reset: 0
Property: Read/Write
Bit 31 30 29 28 27 26 25 24
BUFF_COUNT[15:8]
Access
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
BUFF_COUNT[7:0]
Access
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
DESC_LDST END_BF_ST END_TR_ST CHANN_ACT CHANN_ENB
Access
Reset 0 0 0 0 0
Bits 31:16 – BUFF_COUNT[15:0] Buf
fer Byte Count
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 USBHS device only for the number of bytes needed to complete it.
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 is 0x10000-BUFF_COUNT.
Bit 6 – DESC_LDST Descriptor Loaded Status
Valid until the CHANN_ENB flag is cleared at the end of the next buffer transfer.
Value Description
0
Cleared automatically when read by software.
1
Set by hardware when a descriptor has been loaded from the system bus.
Bit 5 – END_BF_ST End of Channel Buf
fer Status
Valid until the CHANN_ENB flag is cleared at the end of the next buffer transfer.
Value Description
0
Cleared automatically when read by software.
1
Set by hardware when the BUFF_COUNT count-down reaches zero.
Bit 4 – END_TR_ST End of Channel T
ransfer Status
Valid until the CHANN_ENB flag is cleared at the end of the next buffer transfer.
Value Description
0
Cleared automatically when read by software.
1
Set by hardware when the last packet transfer is complete, if the USBHS device has ended the
transfer
.
SAM E70/S70/V70/V71 Family
USB High-Speed Interface (USBHS)
© 2019 Microchip T
echnology Inc.
Datasheet
DS60001527D-page 860