DM9013 datasheet(56/75 Pages) DAVICOM

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DM9013

3-port switch with Processor Interface

Preliminary datasheet

DM9013-15-DS-P03

April 9, 2009

port, see bit 6 of register 61h. The port enters

partition mode when more than 64 consecutive

collisions are occurred. In partition mode the port

continuous to transmit but it will not receive. The port

returned to normal operation mode when a good

packet is seen on the wire. The detail description of

partition mode represent following:

(1). Entering Partition State

A port will enter the Partition State when either of

the following conditions occurs:

The port detects a collision on every one of 64

consecutive re-transmit attempts to the same packet.

The port detects a single collision which occurs

for more than 512 bit times.

Transmit defer timer time out, which indicates

the transmitting packet is deferred to long.

(2). While in Partition state:

The port will continue to transmit its pending

packet, regardless of the collision detection, and will

not allow the usual Back-off Algorithm. Additional

packets pending for transmission will be transmitted,

while ignoring the internal collision indication. This

frees up the ports transmit buffers which would

otherwise be filled up at the expense of other ports

buffers.

The assumption is that the partition is

signifying

system

failure

situation

(bad

connection/cable/station), thus dropping packets is a

small price to pay vs. the cost of halting the switch

due to a buffer full condition.

(3). Exiting from Partition State

The Port exits from Partition State, following the

end of a successful packet transmission.

successful packet transmission is defined as no

collisions were detected on the first 512 bits of the

transmission.

9.2.10 Broadcast Storm Filtering

The DM9013 has an option to limit the traffic of

broadcast or multicast packets, to protect the switch

from lower bandwidth availability.

There are two type of broadcast storm control,

one is throttling broadcast packet only, the other

includes multicast. This feature can be set through bit

1 of register 61h.

The

broadcast

storm

threshold

can

programmed by EEPROM or register 67h, the default

setting is no broadcast storm protecting.

9.2.11 Bandwidth Control

The DM9013 supports two type of bandwidth

control for each port. One is the ingress and egress

bandwidth rate can be control separately, the other is

combined together, this function can be set through

bit 3 of register 61h. The bandwidth control is

disabled by default.

For separated bandwidth control mode, the

threshold rate is defined in register 66h. For

combined mode, it is defined in register 67h.

The behavior of bandwidth control as below:

(1).For the ingress control, if flow control function

is enabled, Pause or Jam packet will be transmitted.

The ingress packets will be dropped if flow control is

disabled.

(2).For the egress control, the egress port will not

transmit any packets. On the other hand, the ingress

bandwidth of source port will be throttled that prevent

packets from forwarding.

(3).In combined mode, if the sum of ingress and

egress bandwidth over threshold, the bandwidth will

be throttled.

9.2.12 Port Monitoring Support

The DM9013 supports “Port Monitoring” function

on per port base, detail as below:

(1). Sniffer Port and Monitor Port

There is only one port can be selected as “sniffer

port” by register 52h, multiple ports can be set as

“receive monitor port” or “transmit monitor port” in

per-port register 65h.

(2).Receive monitor

All packets received on the “receive monitor port”

are send a copy to “sniffer port”. For example, port 0

is set as “receive monitor port” and port 3 is selected

as “sniffer port”. If a packet is received form port 0

and predestined to port 1 after forwarding decision,

the DM9013 will forward it to port 1 and port 3 in the

end.

(3).Transmit monitor

All packets transmitted on the “transmit monitor

port” are send a copy to “sniffer port”. For example,

port 1 is set as “transmit monitor port” and port 3 is

selected as “sniffer port”. If a packet is received from

port 0 and predestined to port 1 after forwarding

decision, the DM9013 will forward it to port 1 and port

3 in the end.

DM9013 Datasheet(PDF) 56 Page - Davicom Semiconductor, Inc.

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