Radyne DMD20 Installation And Operation Manual page 101

DMD20 Universal Satellite Modem
For example, if two DMD20 Modems with different addresses (DESTINATION IDs) are linked to
the same control bus at the same hierarchical level, both will attempt to respond to the M&C
computer when the computer generates a multi-drop override ID of 22. If their actual setup
parameters, status, or internal timing differs, they will both attempt to respond to the override
simultaneously with different information or asynchronously in their respective message packets
and response packets, causing a collision on the serial control bus.
To preclude control bus data contention, different IDs must always be assigned to the equipment.
If two or more devices are configured for direct-linked operation, then the M&C computer and all
other devices configured in the same manner must be programmed to inhibit broadcast of the
corresponding multi-drop override ID.
The multi-drop override ID is always accepted by devices of the same type on a common control
bus, independent of the actual DESTINATION ID. These override IDs with the exception of
"BROADCAST" are responded to by all directly linked devices of the same type causing
contention on the bus. The "BROADCAST" ID, on the other hand, is accepted by all equipment
but none of then returns a response packet to the remote M&C.
The following multi-drop override IDs are device-type specific, with the exception of
"BROADCAST". These are summarized below with ID values expressed in decimal notation:
Directly-Addressed Equipment
Broadcast (all directly-linked devices)
DMD-3000/4000, 4500 or 5000 Mod Section, DMD20
DMD-3000/4000, 4500 or 5000 Demod Section, DMD20
RCU-340 1:1 Switch
RCS -780 1:N Switch
RMUX-340 Cross-Connect Multiplexer
CDS -780 Clock Distribution System
SOM-340 Second Order Multiplexer
DMD-4500/5000 Modulator Section
DMD-4500/5000 Demodulator Section
RCU-5000 M:N Switch
DMD20 Modulator
DMD20 Demodulator
DMD20 Modem
DVB3030 Video Modulator, DM240
RCS20 M:N Switch
RCS10 M:N Switch
RCS11 1:1 Switch
Reserved for future equipment types
TM103 – Rev. 1.1
User Interfaces
Multi-Drop Override ID
00
01
02
03
04
05
06
07
08
09
10
20
21
22
23
24
25
26
27-31
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