Radyne ComStream SFC6400A, Installation And Operation Manual

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User Interfaces SFC6400A/SFC1450A Synthesized Frequency Upconverter
4-24 TM106 – Rev. 1.1
The Communications Specification (COMMSPEC) defines the interaction of computer resident
Monitor and Control software used in satellite earth station equipment such as modems,
redundancy switches, multiplexers, and other ancillary support gear. Communication is bi-
directional, and is normally established on one or more full-duplex multi-drop control buses that
conform to EIA Standard RS-485.
Each piece of earth station equipment on a control bus has a unique physical address, which is
assigned during station setup/configuration or prior to shipment. Valid decimal addresses on one
control bus range from 032 - 255 for a total of up to 224 devices per bus. Address 255 of each
control bus is usually reserved for the M&C computer.
4.4.2.2 RLLP Protocol Wrapper
The Radyne ComStream COMMSPEC is byte-oriented, with the Least Significant Bit (LSB) issued
first. Each data byte is conveyed as mark/space information with two marks comprising the stop
data. When the last byte of data is transmitted, a hold comprises one steady mark (the last stop
bit). To begin or resume data transfer, a space substitutes this mark. This handling scheme is
controlled by the hardware and is transparent to the user. A pictorial representation of the data and
its surrounding overhead may be shown as follows:
S1 S2 B
0
B
1
B
2
B
3
B
4
B
5
B
6
B
7
S1 S2,
etc.
The stop bits, S1 and S2, are each a mark. Data flow remains in a hold mode until S2 is replaced
by a space. If S2 is followed by a space, it is considered a start bit for the data byte and not part of
the actual data (B
0
- B
7
).
The COMMSPEC developed for use with the Radyne ComStream Link Level Protocol (RLLP)
organizes the actual monitor and control data within a shell, or "protocol wrapper", that surrounds
the data. The format and structure of the COMMSPEC message exchanges are described herein.
Decimal numbers have no suffix; hexadecimal numbers end with a lower case h suffix and binary
values have a lower case b suffix. Thus, 22 = 16h = 000010110b. The principal elements of a data
frame, in order of occurrence, are summarized as follows:
<SYN> - the message format header character, or ASCII sync character, that defines the
beginning of a message. The <SYN> character value is always 16h.
<BYTE COUNT> - the Byte Count is the number of bytes in the <DATA> field, ranging from 0 -
TBD.
<SOURCE ID> - the Source Identifier defines the message originator’s multidrop address. Note
that all nodes on a given control bus have a unique address that must be defined.
<DESTINATION ID> - The Destination Identifier specifies the multidrop address of the device(s) to
which the message is sent.
<FRAME SEQUENCE NUMBER> - The FSN is a tag with a value from 0 - 255 that is sent with each
message. It assures sequential information framing and correct equipment acknowledgment and
data transfers.