DP8390D Datasheet, PDF (7/56 Pages) National Semiconductor (TI) – NIC Network Interface Controller

6 0 Direct Memory Access Control (DMA) (Continued)
Dual Bus System
32-Bit DMA Operation
TL F 8582 – 55
TL F 8582 – 6
7 0 Packet Reception
The Local DMA receive channel uses a Buffer Ring Struc-
ture comprised of a series of contiguous fixed length 256
byte (128 word) buffers for storage of received packets The
location of the Receive Buffer Ring is programmed in two
registers a Page Start and a Page Stop Register Ethernet
packets consist of a distribution of shorter link control pack-
ets and longer data packets the 256 byte buffer length pro-
vides a good compromise between short packets and long-
er packets to most efficiently use memory In addition these
buffers provide memory resources for storage of back-to-
back packets in loaded networks The assignment of buffers
NIC Receive Buffer Ring
TL F 8582 – 7
7