AN983B Datasheet, PDF (57/91 Pages) List of Unclassifed Manufacturers – PCI/miniPCI-to-Ethernet LAN Controller

AN983B PCI/miPCI Fast Ethernet Controller with integrated PHY
8.2 NETWORK PACKET BUFFER MANAGEMENT
8.2.1 DESCRIPTOR STRUCTURE TYPES
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.
Ring structure
There are two buffers per descriptor in the ring structure. Support receives early interrupt.
Descriptor
CSR3 or CSR4
Descriptor Pointer
own
Length 2 Length 1
Buffer1 pointer
Buffer2 pointer
Data Buffer
Data
Length 1
Data
Length 2
End of Ring
Fig - 5 Ring structure of frame buffer
Rev. 1.8
ADMtek Inc.
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