adm6995 ETC-unknow, adm6995 Datasheet - Page 25

• Manufacturer Part Number: adm6995
• Description: Port 10/100 Mb/s Single Chip Ethiernet Switch Controller
• Manufacturer: ETC-unknow

ADM6995L
ADMtek Inc.
3.13 Memory Block
3.14 Switch Functional Description
3.15 Basic Operation
ADM6995L build in memory is divided as two blocks. One is MAC addressing table and
another one is data buffer.
MAC address Learning Table size is 2048 entry with each entry occupy eight bytes
length. These eight bytes data include 6 bytes source address, VLAN information, Port
information and Aging counter.
Data buffer is divided to 256 bytes/block. ADM6995L buffer management is per port
fixed block number and all port share one global buffer. This architecture can get better
memory utilization and network balance on different speed and duplex test condition.
Received packet will separate as several 256 bytes/block and chain together. If packet
size more than 256 bytes then ADM6995L will chain two or more block to store
receiving packet.
The ADM6995L uses a “store & forward” switching approach for the following reason:
Store & forward switches allow switching between different speed media (e.g. 10BaseX
and 100BaseX). Such switches require the large elastic buffer especially bridging
between a server on a 100Mbps network and clients on a 10Mbps segment.
Store & forward switches improve overall network performance by acting as a “network
cache”
Store & forward switches prevent the forwarding of corrupted packets by the frame check
sequence (FCS) before forwarding to the destination port.
The ADM6995L receives incoming packets from one of its ports, searches in the Address
Table for the Destination MAC Address and then forwards the packet to the other port
within same VLAN group, if appropriate. If the destination address is not found in the
address table, the ADM6995L treats the packet as a broadcast packet and forwards the
packet to the other ports which in same VLAN group.
The ADM6995L automatically learns the port number of attached network devices by
examining the Source MAC Address of all incoming packets at wire speed. If the Source
Address is not found in the Address Table, the device adds it to the table.
Function Description
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