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User Interfaces
Multi-drop override ID 01 can be used interchangeably to broadcast a
message to a DMD-3000/4000 modem, a DMD-4500/5000, a DMD15 modem,
or a DVB3030. Radyne Corp. recommends that the multi-drop override IDs
be issued only during system configuration as a bus test tool by
experienced programmers, and that they not be included in run-time
software. It is also advantageous to consider the use of multiple bus
systems where warranted by a moderate to large equipment complement.
Therefore, if a DMD15 Modulator is queried for its equipment type identifier, it will return a "20"
and DMD15 Demodulator will return a "21". A DMD15 Modem will also return an "22". A
DVB3030 Video Modulator will return a "23."
4.9.6 Software Compatibility
The COMMSPEC, operating in conjunction within the RLLP shell, provides for full forward and
backward software compatibility independent of the software version in use. New features are
appended to the end of the DATA field without OPCODE changes. Older software simply
discards the data as extraneous information without functional impairment for backward
compatibility.
If new device-resident or M&C software receives a message related to an old software
version, new information and processes are not damaged or affected by the omission of data.
The implementation of forward and backward software compatibility often, but not always,
requires the addition of new Opcodes. Each new function requires a new Opcode assignment if
forward and backward compatibility cannot be attained by other means.
When Radyne equipment is queried for bulk information (Query Mod, Query Demod, etc.) it
responds by sending back two blocks of data; a Non-Volatile Section (parameters that can be
modified by the user) and a Volatile Section (status information). It also returns a count value that
indicates how large the Non-Volatile Section is. This count is used by M&C developers to index
into the start of the Volatile Section.
When new features are added to Radyne equipment, the control parameters are appended to the
end of the Non-Volatile Section, and status of the features, if any, are added at the end of the
Volatile Section. If a remote M&C queries two pieces of Radyne equipment with different revision
software, they may respond with two different sized packets. The remote M&C must make use of
the non-volatile count value to index to the start of the Volatile Section. If the remote M&C is not
aware of the newly added features to the Radyne product, it should disregard the parameters at
the end of the Non-Volatile Section and index to the start of the Volatile Section.
If packets are handled in this fashion, there will also be backward-compatibility between Radyne
equipment and M&C systems. Remote M&C systems need not be modified every time a feature
is added unless the user needs access to that feature.
4-22
DM240-DVB High-Speed Digital Modulator
TM083 - Rev. 3.0
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