Operating instructions

DVB3030/DVB3030L Digital Video Broadcast Modulator User Interfaces
TM052 - Rev. 3.5 4-21
4.3 Remote Port User Interface
The Remote Port of the DVB3030 allows for complete control and monitor functions via an
RS-485 Serial Interface.
Control and status messages are conveyed between the DVB3030 and the subsidiary modems
and the host computer using packetized message blocks in accordance with a proprietary
communications specification. This communication is handled by the Radyne Link Level
Protocol (RLLP), which serves as a protocol ‘wrapper’ for the M&C data.
Complete information on monitor and control software is contained in the following sections.
4.3.1 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 9600 baud 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.
4.3.2 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 (00h) 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 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 DVB3030 protocol.