AN985B/BX
Functional Descriptions
7
Functional Descriptions
7.1
Network Packet Buffer Management
7.1.1
Descriptor Structure Types
For networking operations, the AN985B/BX transmits the data packet from transmitting buffers in host memory to
AN985B/BX’s transmitting FIFO and receives the data packet from AN985B/BX’s receiving FIFO to receive buffers
in host memory. The descriptors that the AN985B/BX supports to build in host memory are used as the pointers
of these transmitting and receiving buffers.
There are two structure types for the descriptor, Ring and Chain, supported by the AN985B/BX and are shown
as below. The type selections are controlled by bit 24 of RDES1 and the bit 24 of TDES1.
The transmitting and receiving 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.
Figure 4
Chain structure
There is only one buffer per descriptor in the chain structure.
Ring Structure of Frame Buffer
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Data Sheet
18
Rev. 1.51, 2005-11-30
INFINEON [ Infineon ]
