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WI-MOD-9-D
Radio Modem
User Manual v1.9
WI-MOD-9-D
Manual
v 1.9
Page
24
3.6
Controlled Mode
In controlled mode, data is only transferred between two modules (that is, a point to point link).
One of the modules is configured as a “master” unit and the other as a “slave” unit. There can
also be up to five intermediate repeaters in the link. Each WI-MOD-9-D unit is configured with
a unit address - only the unit with an address matching the destination address of the radio
message will process the message and output the serial data.
To establish a link, the master will transmit a special “connect” message. This initial message
will not include any data. If the “slave” unit receives the initial message, and is not already
connected to another WI-MOD-9-D unit, it will return an acknowledgment message. Both units
will activate their DCD LED, and also activate their DCD signal. If the master unit does not
receive the acknowledgment, the DCD output will reset. When the connection is made (DCD
set), the WI-MOD-9-D units can transmit data to each other.
Once the communications channel has been established, the WI-MOD-9-D unit will accept input
data and send radio messages with data. When a WI-MOD-9-D unit receives a radio message, it
will check the system address and destination address, and also the error-check (optional). If
these are correct, it will return a ACK (acknowledgment) message to the source unit. If the
system address or destination address is not correct, or if the error-check is not correct, then no
return message is sent.
Establishing a Communications Link
Master Unit
Slave Unit
•
Listen to ensure channel is clear
•
If clear, transmit “connect”
message
•
Radio TX LED flashes
----------------->
•
Receives message
•
Radio RX LED flashes
•
Check system and destination
address
•
If OK, set DCD LED and
output
•
Radio RX LED flashes
<-----------------
•
If message OK, transmit back
an ACK message.
•
Radio TX LED flashes
•
Acknowledgment received okay
communication link established
•
Set DCD LED and output
If the source unit does not receive an ACK message, it will re-transmit the same message. It will
attempt to transmit the message up to five times. If the unit still does not receive an ACK
message after five attempts, it will reset the DCD LED, and reset the DCD output.