DP8390 NSC [National Semiconductor], DP8390 Datasheet - Page 7

• Manufacturer Part Number: DP8390
• Description: NIC Network Interface Controller
• Manufacturer: NSC [National Semiconductor]

6 0 Direct Memory Access Control (DMA)
(Continued)
Dual Bus System
TL F 8582 – 55
32-Bit DMA Operation
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
TL F 8582 – 6
NIC Receive Buffer Ring
TL F 8582 – 7
7