19 udphs dma channel status register – Rainbow Electronics AT91CAP9S250A User Manual
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6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
44.5.19
UDPHS DMA Channel Status Register
Name:
UDPHS_DMASTATUSx [x = 1..6]
Access Type: Read/Write
• CHANN_ENB: Channel Enable Status
0 = if cleared, the DMA channel no longer transfers data, and may load the next descriptor if the UDPHS_DMACONTROLx
register LDNXT_DSC bit is set.
When any transfer is ended either due to an elapsed byte count or a UDPHS device initiated transfer end, this bit is auto-
matically reset.
1 = if set, the DMA channel is currently enabled and transfers data upon request.
This bit is normally set or cleared by writing into the UDPHS_DMACONTROLx register CHANN_ENB bit field either by soft-
ware or descriptor loading.
If a channel request is currently serviced when the UDPHS_DMACONTROLx register CHANN_ENB bit is cleared, the
DMA FIFO buffer is drained until it is empty, then this status bit is cleared.
• CHANN_ACT: Channel Active Status
0 = the DMA channel is no longer trying to source the packet data.
When a packet transfer is ended this bit is automatically reset.
1 = the DMA channel is currently trying to source packet data, i.e. selected as the highest-priority requesting channel.
When a packet transfer cannot be completed due to an END_BF_ST, this flag stays set during the next channel descriptor
load (if any) and potentially until UDPHS packet transfer completion, if allowed by the new descriptor.
• END_TR_ST: End of Channel Transfer Status
0 = cleared automatically when read by software.
1 = set by hardware when the last packet transfer is complete, if the UDPHS device has ended the transfer.
Valid until the CHANN_ENB flag is cleared at the end of the next buffer transfer.
• END_BF_ST: End of Channel Buffer Status
0 = cleared automatically when read by software.
1 = set by hardware when the BUFF_COUNT downcount reach zero.
Valid until the CHANN_ENB flag is cleared at the end of the next buffer transfer.
• DESC_LDST: Descriptor Loaded Status
31
30
29
28
27
26
25
24
BUFF_COUNT
23
22
21
20
19
18
17
16
BUFF_COUNT
15
14
13
12
11
10
9
8
–
–
–
–
–
–
–
–
7
6
5
4
3
2
1
0
–
DESC_LDST
END_BF_ST
END_TR_ST
–
–
CHANN_ACT
CHANN_ENB