Software Compatibility - Radyne DMD20 Installation And Operation Manual

User Interfaces DMD20 Universal Satellite Modem
Note that multi-drop override IDs 01 or 02 can be used interchangeably to broadcast a message
to a DMD-3000/4000 Modem, DMD-4500/5000, or a DMD20 Modem. Radyne ComStream
Corporation 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 DMD20 Modulator is queried for its equipment type identifier, it will return a "20"
and DMD20 Demodulator will return a "21". A DMD20 Modem will also return a "22".

4.9.1.6 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 soft ware 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 ComStream Corporation 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 the size of the Non-Volatile Section. This count is used by
M&C developers to index into the start of the Volatile Section.
When new features are added to Radyne ComStream 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 ComStream
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
ComStream 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
ComStream Corporation 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.
4-54 TM103 - Rev. 1.1