Some Common Commands; Remote Control Protocol And Structure; Rs-485 - Comtech EF Data C Installation And Operation Manual

HPOD
Customer Commands
4.7 S C
OME OMMON
A few of the most common commands and queries are listed below. Full details for each
of these are listed at the end of this section.
• RMS = Retrieve Maintenance Status. Displays voltages, fan speeds, Heatsink
temperature, output power monitor reading, etc.
• RCS = Retrieve Configuration Status. Displays current attenuation, mute,
amplifier, online, etc. status.
• RAS = Retrieve Alarm Status. Displays current alarm or fault status.
4.8 R C
EMOTE
This section describes the protocol and message command set for remote monitor and
control of the SSPA product.
The electrical interface is either an RS-485 multi-drop bus (for the control of many
devices) or an RS-232 connection (for the control of a single device), and data is
transmitted in asynchronous serial form, using ASCII characters. Control and status
information is transmitted in packets of variable length in accordance with the structure
and protocol defined in later sections.

4.9 RS-485

For applications where multiple devices are to be monitored and controlled, a full-duplex
(4-wire) RS-485 is preferred. Half-duplex (2-wire) RS-485 is possible, but is not
preferred.
In full-duplex RS-485 communication there are two separate, isolated, independent,
differential-mode twisted pairs, each handling serial data in different directions. It is
assumed that there is a 'controller' device (a PC or dumb terminal), which transmits data,
in a broadcast mode, via one of the pairs. Many 'target' devices are connected to this
pair, which all simultaneously receive data from the controller. The controller is the only
device with a line-driver connected to this pair; the target devices only have line-
receivers connected.
In the other direction, on the other pair, each target has a tri-stateable line driver
connected, and the controller has a line-receiver connected. All the line drivers are held in
high-impedance mode until one (and only one) target transmits back to the controller.
C
OMMANDS
P
ONTROL ROTOCOL AND
S
TRUCTURE
4–3
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MN/HPOD.IOM