User's Manual

MDS 05-2708A01, Rev. A MDS TransNET I/O Guide 19
Software Programming (TDD Command)
As with other repeater systems, the network must be configured for TDD
operation by programming the master radio with TDD ON. This places the DATA
INTERFACE port in time division duplex (sometimes called “simulated
full-duplex”) mode.
Although a single radio can never actually transmit and receive RF data at the
same time, the
TDD ON command enables the radio to simulate full-duplex at
the data port, by designating alternate channel hops as transmit or receive hops,
and buffering data when transmission is not permitted.
Limitations of Single-Radio Repeaters
Diagnostics As of the date of publication, over-the-air diagnostics is not fully supported in
repeater systems. Diagnostic data from these systems may be unavailable or
unreliable. This is particularly true if a repeater radio is configured as the
“root” in a diagnostics scheme. Better success might be achieved by picking a
standard remote to use as the root.
Data Throughput De-
lay
When TDD is set to ON, there will be a significant delay in data throughput and
an increase in latency (see Glossary of Terms). In general, the data throughput
will be cut in half, and worst case latency will increased by two hop times.
5.5 Using the Radio’s Sleep Mode
In some installations, such as at solar-powered sites, it may be necessary to
keep the transceiver’s power consumption to an absolute minimum. This can
be accomplished using Sleep Mode. In this mode, power consumption is
reduced to less than 5 milliamperes.
Sleep Mode can be enabled under RTU control by asserting a ground (or
EIA-232 low) on Pin 4 of the radio’s
DATA INTERFACE connector. The radio
stays in Sleep Mode until the low is removed, and all normal functions are
suspended. As a status indication, the radio’s PWR LED flashes once every
four seconds to indicate that it is in Sleep Mode.
The radio can be “woken up” by your RTU every minute or so to verify
synchronization with the master station. When Pin 4 is opened (or an EIA-232
high is asserted), the radio will be ready to receive data within 75 milliseconds.
It is important to note that power consumption will increase significantly as
communication from the master station degrades. This is because the radio will
spend a greater period of time “awake,” looking for synchronization messages
from the master radio.
Sleep Mode Example
The following example describes Sleep Mode implementation in a typical
system. Using this information, you should be able to configure a system that
meets your own particular needs.
Suppose you need communications to each remote site only once
per hour. Program the RTU to raise an EIA-232 line once each hour
(DTR for example) and wait for a poll and response before lower-
ing it again. Connect this line to Pin 12 of the radio’s
DATA INTER-
FACE connector. This will allow each RTU to be polled once per
hour, with a significant savings in power consumption.