adm6996f Infineon Technologies Corporation, adm6996f Datasheet - Page 27

• Manufacturer Part Number: adm6996f
• Description: 6 Port 10/100 Mb/s Single Chip Ethernet Switch Controller
• Manufacturer: Infineon Technologies Corporation

ADM6996F
Infineon-ADMtek Co Ltd.
3.14 Switch Functional Description
3.15 Basic Operation
3.15.1 Address Learning
The ADM6996F 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 ADM6996F 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 ADM6996F treats the packet as a broadcast packet and forwards the
packet to the other ports which in same VLAN group.
The ADM6996F 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.
The ADM6996F uses a hash algorithm to learn the MAC address and can learn up to 2K
MAC addresses. Address is stored in the Address Table. The ADM6996F searches for
the Source Address (SA) of an incoming packet in the Address Table and acts as below:
If the SA was not found in the Address Table (a new address), the ADM6996F waits until
the end of the packet (non-error packet) and updates the Address Table. If the SA was
found in the Address Table, then aging value of each corresponding entry will be reset to
0.
When the DA is PAUSE command, then the learning process will be disabled
automatically by ADM6996F.
Function Description
3-9