D M A c h a n n e l r e g i s t e r s

Buffer Descriptor Pointer register

Address: FF90 0000 / 20 / 40 / 60 / 80 / A0 / C0 / E0 / 100 / 120 / 140 / 160 / 180 / 1A0 / 1C0 / 1E0

The Buffer Descriptor Pointer register contains the address of the first buffer descriptor in a contiguous list of descriptors.

DMA channel 1 is unique in that it supports four different buffer descriptors: A, B, C, and D. Each buffer descriptor contains a separate ring of descriptors, and identifies a block of data buffers with a different size. This feature allows the Ethernet receiver to choose the optimum buffer size for the incoming packet.

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Buffer descriptor pointer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Buffer descriptor pointer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DMA Control register

Address: FF90 0010 / 30 / 50 / 70 / 90 / B0 / D0 / F0 / 110 / 130 / 150 / 170 / 190 / 1B0 / 1D0 / 1F0

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CE

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BTE

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RSVD

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Reserved

 

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N S 7 5 2 0 H a r d w a r e R e f e r e n c e , R e v . D 0 3 / 2 0 0 6

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Image 150
Digi NS7520 manual Buffer Descriptor Pointer register, DMA Control register