MX-2100/2104
Installation and Operation Manual
Chapter 1 General Information
Application Considerations
1-27
In the application shown in
, the multidrop channel of the KDI module
is used to connect between the host computer (connected to a data channel of a
KLS.1/NEW module installed in MX-2100 situated at the central site), and several
data terminals located at other locations. The communication is based on a polled
protocol, whereby the host operates as the master and arbitrates the traffic on the
multidrop link by addressing the Dates one at a time. The multidrop feature
operates as follows:
•
All the Dates connected along the link can receive the data sent by the host,
because all the multidrop channels of all MX-2100 are allocated bandwidth on
link A. In addition, the bandwidth allocated to the multidrop channels is also
designated for bypassing to link B, to enable all the downstream Dates to
receive the host.
•
When a DTE connected to a KDI/M module has data to transmit toward the
host, it must assert its RTS line. The assertion of the RTS line in the multidrop
channel interface changes the routing of the main link data by the
corresponding KDI/M module:
−
The KDI/M module disconnects the bypassing connection of the multidrop
channel data to main link B, and the channel data is dropped locally. As
long as the RTS line is asserted, the DTE remains connected to main link A,
just as in a point-to-point connection.
−
When the RTS line is deasserted (at the end of DTE transmission), the
KDI/M module stops dropping the channel data, and the bypassing path is
re-established.
HOST
KML
MX-2100
KC
L
KD
I
KML
A
KML
B
MX-2100
KCL
KDI
KML
A
KML
B
MX-2100
KCL
KDI
KML
A
KML
B
MX-2100
KCL
KDI
DTE
DTE
DTE
KL
S.
1
Figure 1-16. Typical KDI Bypassing and Multidrop Application
Priority Bumping (not for MX-2104)
With optional point-to-point dual-link configurations, such as shown in
MX-2100 allows to provide the equivalent of hot-standby protection
to critical data channels, without paying for unutilized bandwidth. This feature is
called
priority bumping.