rtd DM35820HR, Руководство пользователя

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| www.rtd.com 73 DMx820 User’s Manual
Bit Description Read Write Value
after
Reset
Value
to Use
22:0 Transfer Size (Bytes). Indicates the number
of bytes to transfer during a DMA operation.
Yes Yes 0h x
30:23 Reserved Yes No 0h 0h
31 Ring Management Valid. When Ring
Management Valid Mode is enabled
(DMAMODE0[20]=1), indicates the validity of
this DMA descriptor.
Yes Yes 0 x
DMAPRn
DMA Channel n Descriptor Pointer
Bit Description Read Write Value
after
Reset
Value
to Use
0 Descriptor Location. Writing 1 indicates PCI
Address space. Writing 0 indicates Local
Address space.
Yes Yes 0h 1
1 End of Chain. Writing 1 indicates end of
chain. Writing 0 indicates not end of chain
descriptor. (Same as DMA Block mode.)
Yes Yes 0h x
2 Interrupt after Terminal Count. Writing 1
causes an interrupt to be asserted after the
terminal count for this descriptor is reached.
Writing 0 disables interrupts from being
asserted.
Yes Yes 0h x
3 Direction of Transfer. Writing 1 indicates
transfers from the Local Bus to the PCI Bus.
Writing 0 indicates transfers from the PCI Bus
to the Local Bus.
Yes Yes 0h x
31:4 Next Descriptor Address. X0h-aligned
(DMADPR0[3:0]=0h).
Yes Yes 0h x
DMACSRn
DMA Channel n Command/Status
Bit Description Read Write Value
after
Reset
Value
to Use
0 Enable. Writing 1 enables the channel to
transfer data. Writing 0 disables the channel
from starting a DMA transfer, and if in the
process of transferring data, suspends the
transfer (pause).
Yes Yes 0h 1
1 Start. Writing 1 causes the channel to start
transferring data if the channel is enabled.
Yes Yes/
Set 0h x