DP83256 datasheet(21/144 Pages) NSC

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30 Functional Description (Continued)

CONCENTRATOR CONFIGURATIONS

There are 2 types of concentrators Single Attach and Dual

Attach These concentrators can be designed with or with-

out MAC(s) The configuration is determined based upon its

type and the number of active MACs in the concentrator

Using the PLAYERa device a concentrator can be built

with many different configurations without any external log-

The DP83256 DP83256-AP and DP83257 can be used to

build a Single Attach concentrator

See Application Note AN-675 Designing FDDI concentra-

tors and Application Note AN-741 Differentiating FDDI con-

centrators for further information

Concepts

A concentrator is comprised of 2 parts the Dual Ring Con-

nect portion and the Master Ports

The Dual Ring Connection portion connects the concentra-

tor to the dual ring directly or to another concentrator If the

concentrator is connected directly to the dual ring it is a

part of the ‘‘Dual Ring of Trees’’ If the concentrator is con-

nected to another concentrator it is a ‘‘Branch’’ of the

‘‘Dual Ring of Trees’’

The Master Ports connect the concentrator to its ‘‘Slaves’’

or S-class Single Attach connections A slave could be a

Single Attach Station or another concentrator (thus forming

another Branch of the Dual Ring Tree)

When a MAC in a concentrator is connected to the primary

or secondary ring it is required to be situated at the exit port

of that ring (ie its PH

IND is connected to the IND Inter-

face of the last Master Port in the concentrator (PHY

Mn)

that is connected to that ring)

A concentrator can have two MACs one connected to the

primary ring and one to the secondary ring In addition rov-

ing MACs can be included in the concentrator configuration

A roving MAC can be used to test the stations connected to

the concentrator before allowing them to join the dual ring

This may require external multiplexers if used in conjunc-

tion with two other MAC layers

Single Attach Concentrator

A Single Attach concentrator is a concentrator that has only

one PHY at the dual ring connect side It cannot therefore

be connected directly to the dual ring A Single Attach con-

centrator is a branch to the dual ring tree It is connected to

the ring as a slave of another concentrator

Multiple Single Attach concentrators can be connected to-

gether hierarchically to build a multiple levels of branches in

a dual ring

The Single Attach concentrator can be connected to either

the primary or secondary ring depending on the connection

with its concentrator (the concentrator that it is connected

to as a slave)

Figure 3-15 shows a Single Attach concentrator with a sin-

gle MAC

Dual Attach Concentrator

A Dual Attach concentrator is a concentrator that has two

PHYs on the dual ring connect side It is connected directly

to the dual ring and is a part of the dual ring tree

The Dual Attach concentrator is connected to both the pri-

mary and secondary rings

Dual Attach Concentrator with Single MAC

Figure 3-16 shows a Dual Attach concentrator with a single

MAC

Because the concentrator has one MAC it can only transmit

and receive frames on the ring to which the MAC is con-

nected The concentrator can only repeat frames on the

other ring

Dual Attach Concentrator with Dual MACs

Figure 3-17 shows a Dual Attach concentrator with dual

MACs

Because the concentrator has two MACs it can transmit

and receive frames on both the primary and secondary

rings

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