AN983 datasheet(57/91 Pages) ETC

57 / 91 page

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.

Buffer2 pointer

Buffer1 pointer

Length 1

Length 2

End of Ring

own

CSR3 or CSR4

Data

Descriptor Pointer

Data Buffer

Length 1

Length 2

Descriptor

Fig -

Ring structure of frame buffer

ADMtek Inc.

www.admtek.com.tw

Rev. 1.8

AN983 데이터시트(PDF) 57 Page - List of Unclassifed Manufacturers