USER MANUAL, MSD-4, PT# 101012
P a g e
|
3
EAST COAST DATACOM, INC.
2.5
SUB
‐
CHANNEL
CONTENTION
MODES
2.5.1 Sub-channel SCANNING Mode
The
Scanning
Mode
will allow equal access to the communications link for all connected DTE
devices. The Sub-channels are scanned in sequence (1 - 2 - 3 - 4) and the attached sub-channel
DTE that raises RTS will have access to the communications link. After dropping RTS the MSD
will continue scanning in sequential order.
2.5.2 Sub-channel PRIORITY Mode
The
Priority
Mode
allows the user to have channel 1 as the highest priority channel to service the
communications link. The Sub-channels are continually monitored. If channel 2 or 3 raises RTS
and transmits data and then drops RTS, sub-channel 1 will have the highest priority over the
next port that raises RTS, (if sub-channel 1 has information to transmit). This will allow a DTE
that has more important information to send or retrieve from the host a higher priority.
2.5.3 Sub-channel SWITCH ON DATA
The Switch on Data Mode allows an attached sub-channel DTE device to access the Master Port
when data is sent. In this mode of operation, the network must be disciplined as that no two sub-
channels can communicate back to the host at the same time.
2.6
DATA
BROADCAST
ONLY
APPLICATIONS
The MSD-4 may be used in Data/Clock Broadcast applications. This can be accomplished by
several methods.
One:
Disable the Front Panel switches and RXD and Clock from the Master Port
will always continue outbound to all sub-channels. And data cannot be sent back to the Master
Port.
Two:
Remove Pin 2 TXD from the attached sub-channel cables, data and clock will always
be broadcast to all sub-channels.
NOTE:
The front Panel LED’s will show RXD and DCD if sent by the Master Port to the sub-
channels. The
Port
Active
LED’s
will not illuminate in a broadcast only application.
2.7
ANTI
‐
STREAMING
2.7.1 Automatic DTE Removal
The MSD-4 incorporates circuitry that will (when enabled)
automatically
remove a streaming
terminal from service. A streaming terminal is defined as a terminal that has RTS
high
longer
than the user predefined anti-stream timer has been set. Upon installation, the user can set or
actually fine tune the timer to your network requirements. Each channel has a Green and a
Yellow LED to indicate sub-channel activity. Green indicates an active sub-channel and Yellow
indicates a streaming sub-channel. Once a terminal has gone into the streaming condition (RTS
continually high) the DTE will automatically be removed from service until the DTE fault has
