AN983 ETC [List of Unclassifed Manufacturers], AN983 Datasheet - Page 57

• Manufacturer Part Number: AN983
• Description: PCI/miniPCI-to-Ethernet LAN Controller
• Manufacturer: ETC [List of Unclassifed Manufacturers]

8.2 NETWORK PACKET BUFFER MANAGEMENT
8.2.1 DESCRIPTOR STRUCTURE TYPES
Rev. 1.8
For networking operation, the AN983B transmits the data packet from transmit buffers in host
memory to AN983B’s transmit FIFO and receives the data packet from AN983B’s receive FIFO to
receive buffers in host memory. The descriptors that the AN983B supports to build in host memory
are used as the pointers of these transmit and receive buffers.
There are two structure types for the descriptor, Ring and Chain, supported by the AN983B and are
shown as below. The type selection is controlled by the bit24 of RDES1 and the bit24 of TDES1.
The transmit and receive buffers are physically built in host memory. Any buffer can contain either a
whole packet or just part of a packet. But it can’t contain more than one packet.
There are two buffers per descriptor in the ring structure. Support receives early interrupt.
Ring structure
Descriptor Pointer
CSR3 or CSR4
End of Ring
Fig - 5 Ring structure of frame buffer
Descriptor
AN983B
own
Buffer1 pointer
Buffer2 pointer
www.admtek.com.tw
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PCI/miPCI Fast Ethernet Controller with integrated PHY
Data Buffer
Data
Data
Length 1
Length 2
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