Radyne DM240XR Specifications download pdf (Page 53)

DM240XR High-Speed Digital Modulator User Interfaces

MN-DM240XR– Revision 13 4–31

Complete information on monitor and control software is contained in the following sections.

4.4.1 Protocol Structure

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 through 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 Protocol Wrapper

The Radyne 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:

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

- B

The COMMSPEC developed for use with the Radyne 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

through TBD. This field is 2 bytes long for the DM240 protocol.

<SOURCE ID> - the Source Identifier defines the message originator’s multidrop address.

1 2 ... 48 49 50 51 52 53 54 55 56 57 58 ... 195 196

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Radyne DM240XR Specifications Page 53