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2-30
ACTIVATING A CONFIGURATION
A configuration actually controls the multiplexing process when it is activated. The configuration
may be activated immediately by a MEGAMUX PLUS operator, or automatically, at a time and
date specified by the Activate a TDM Configuration routine.
When a configuration is activated, all channel parameters are transferred from non-volatile memory
to data memory (RAM) on the AUTO FRAME module. The AUTO FRAME module then performs
a framing calculation, determining the sequence of channel data, control, and over-head bit select
codes for the frame. This activity occurs at both the Node M and Node S TDMs, under the control
of the Node M system. When both TDMs have calculated the frame, the frame is distributed into
memory at each TDM site. The channel parameters are also distributed to the channel modules at
each node; the channel modules are set to operate according to circuit type and related parameters.
All modules are set to operate at the baud rates selected by the configuration. Identical transmit and
receive frames are stored at each node. The Node M TDM then instructs the Node S TDM to switch
over to the new frame; the switch is done simultaneously by each node. Data is multiplexed accord-
ing to the frames created for the newly activated configuration.
If the TDM loses synchronization, the data frame is no longer used; the system reverts to a sync
frame until synchronization is restored. When the sync frame is being used, no channel operations
can occur, because no channels are defined in the sync frame. When the TDMs achieve synchroni-
zation again, the previously active configuration becomes active again.
When you change channel parameters for a configuration, the new parameters are stored in non-
volatile memory as part of the configuration. If you are adding parameters to the configuration that
is active, those parameters do not become operational until the configuration is re-activated. The
new parameter data is then considered in the framing process, and distributed to channel modules.
MULTI-DROP TERMINAL SYSTEM
The AUTO FRAME module may be configured to support a multi-drop terminal system, where up
to 8 TDM links may be controlled by a single CRT. Each MEGAMUX PLUS node connected to a
multi-drop CRT must be located at the same site as the CRT, with no more than 50 feet of cable
between the CRT and any MEGAMUX PLUS unit. A communications link may not be used to con-
nect a multi-drop CRT and a MEGAMUX PLUS node. Note that all controllers located at the TDM
do not have to be masters
Each TDM link in the system is identified by a letter from A to H. Switch S2 on the AUTO FRAME
module must be set to the node address; the switch setting is determined by the binary numerical
equivalent of the letter identifier. Table 2-3 lists the switch settings for each node address.
For a single link system, set all S2 switch positions on the AUTO FRAME module Up (binary 31)
or Down (binary 0).
To select a particular TDM unit, you depress the Control and P keys simultaneously (Control P) and
then enter the letter address of the particular TDM system. The CRT then displays the MEGAMUX
PLUS main menu; you are now communicating with the selected MEGAMUX PLUS link. The sta-
tus line reports which TDM is presently communicating with the CRT and, at the same time, reports
the active config-uration status.
036R660-000, Issue 10
NOTE
Do not use settings with a binary value of 9 through 30; some of these
values are indeterminate. Do not use the same identifier (TDM
Identification letter) for two different TDMs; this will result in an
unpredictable display.
System Overview
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