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DM8108

8 port 10/100M Fast Ethernet Switching Controller

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DM8108

8 port 10/100M Fast Ethernet Switching Controller

Packet Routing

As any port in the DM8108 receives a packet, the DM8108

will put the received data in the receiving buffer and start the

address recognition at same time.

The DM8108 is targeted for the non-managed Ethernet

Switching application. No management functions provided.

DRAM Interface

1. If the destination address is pointed to a local port

other than receiving port, the DM8108 will update the

Transmit Descriptor of the target port with the buffer

location and byte count information and wait for

transmission.

2. If the destination address is pointed to a port located in

other devices, the DM8108 will update the

Transmit Descriptor of the expansion port with the

receiving buffer location and byte count information

and wait for transmission.

3.

f the destination address is not found in the Address

Table, the DM8108 will update all the Transmit

Descriptors, except the one of the receiving port, for

transmission.

4. For the Multicast/Broadcast addresses, the DM8108

simply updates all the Transmit Descriptors, except

the one of the receiving port or the ports that are

disabled, for Transmission.

5. For bad packet, the DM8108 simply discards it.

6. If the receiving buffer or the Transmit Descriptor for a

particular port is full, the packet will be lost.

The DM8108 interfaces to 1M or 2M bytes of SGRAM or

SDRAM. The DRAM is used to store incoming packets as

well as he address table and Transmit Descriptors. The

DRAM can operate at up to 90MHz. One 256kx32 or

512kx16 SGRAM are required respectively for 1M or 2M

shared memory size.

Expansion Bus

The expansion bus contains Receive Port and Transmit I

Port. Each port is 4-bit wide.

The Receive Port takes the incoming packet into a FIFO

that has to be distributed to the Receiving Buffer

immediately. At the same time, the DM8108 will check the

destination and source addresses to determine the target

port and update the Address Table if necessary.

The Transmit Port is dedicated for transferring packets out

to other switching members if the Transmit Descriptor for

this port saying the transmission is pending.

Network Management Features

Total of 8-DM8108 can be cascaded for a 64-port switching

system.

Preliminary

11

Version: DM8108-DS-P02

November 25, 1999

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