dp83251 National Semiconductor Corporation, dp83251 Datasheet - Page 13

• Manufacturer Part Number: dp83251
• Description: Player Device Fddi Physical Layer Controller
• Manufacturer: National Semiconductor Corporation

3 0 Functional Description
CONCENTRATOR CONFIGURATIONS
There are 2 types of Concentrators Single Attach and Dual
Attach These Concentrators can be designed with or with-
out the MAC(s) Its configuration is determined based upon
its type and the number of active MACs in the Concentrator
Using the PLAYER devices a Concentrator can be built with
many different configurations without the need of any exter-
nal logic
Both the DP83251 and DP83255 can be used to build a
Single Attach Concentrator Only the DP83255 is recom-
mended for the Dual Attach Concentrator design
See Application Note 675 Designing FDDI Concentrators
and Application Note 741 Differentiating FDDI Concentra-
tors for futher 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 Tree’’ If the Concentrator is connect-
ed to another Concentrator it is a ‘‘Branch’’ of the ‘‘Dual
Ring Tree’’
The Master Ports connect the Concentrator to its ‘‘Slaves’’
A Slave could be a Single Attach Station or another Con-
centrator (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 concentrator (i e its PH IND is connected to
the IND Interface of the last Master Port in the Concentrator
(PHY M n) that is connected to that ring)
A Concentrator can have two MACs connected to both the
Primary and Secondary rings In addition a Roving MAC can
be included in the Concentrator configuration A Roving
MAC can be used to test the stations connected to the Con-
centrator before allowing them to join the Dual Ring This
may require external multiplexers
(Continued)
13
Figure 3-10 shows a Single Attach Concentrator with a Sin-
Figure 3-11 shows a Dual Attach Concentrator with a Single
Figure 3-12 shows Dual Attach Concentrator wih Dual
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 Concentrator 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 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 a slave)
gle MAC
Dual Attach Concentrator
A Dual Attach Concentrator is a Concentrator that has two
PHYs at 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
MAC
Because the Concentrator has one MAC it can only trans-
mit and receive frames on the ring where the MAC is con-
nected The Concentrator can only repeat frames on the
other ring
Dual Attach Concentrator with Dual MACs
MACs
Because the Concentrator has two MACs it can transmit
and receive frames on both the Primary and Secondary
rings