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WI-MOD-9-D
Radio Modem
User Manual v1.9
WI-MOD-9-D
Manual
v 1.9
Page
20
3.2.2 Serial Data Rate
The communications baud rates supported on both the RS232 serial port and the RS485 serial port
are 1200, 2400, 4800, 9600, 14400, 19200, 28800, 31250, 38400, 57600, 76800 and 115200 baud -
the user selects one of these rates during the configuration of the modem.
3.2.3 Radio Data Rate
The data is transmitted by radio as direct modulated synchronous data at 19200, 57600 or
115200 bits/second. The user must configure the radio data rate at each WI-MOD-9-D module.
The configured radio data rates must be the same for each module in a system.
At 19200 and 57600 bits/sec, the WI-MOD-9-D adds forward error correction in the transmitted
data. This is added automatically and is different to the configurable CRC error-check.. The
radio range at 19200 baud is better than 57600 or 115200. The expected range at 57600 is 60%
of maximum and at 115200 is 30%.
The radio message includes the following :-
•
A 30 msec leading sequence of alternating 1’s and 0’s provides the receiving unit with
time to capture and lock onto the incoming signal. This time is reduced to 5msec for the “fast”
controlled mode option (point-to-point only).
•
A system address is superimposed on each message to provide discrimination between
different WI-MOD-9-D systems on the same radio channel. Each WI-MOD-9-D unit in the same
system must be configured with the same system address - refer Section 4, Configuration.
Although other WI-MOD-9-D modules may hear the radio transmissions, because they have a
different system address, the radio transmission is ignored and no serial data is output.
•
In transparent mode, a group address is included, and in controlled mode, unit
addressing is included.
An error-check (16 bit CRC) may be configured by the user.
Up to 530 bytes of data may be transmitted in a message - the maximum message size is
configurable between 10 and 530 bytes. The data consists of a sequence of 8 bit bytes. Start,
stop and parity bits are not transmitted, but they are re-generated at the receiving unit (if
configured).
A “transmit delay” time and a “receive delay” time may also be configured. These parameters may
be used to fine tune and give priority to different WI-MOD-9-D units in a system.
•
After each message is transmitted, a WI-MOD-9-D unit will not transmit another message
during the transmit delay time. This could be used to allow a reply message to be received
before the next message is sent. This delay is a different delay to the delay introduces by the
WI-MOD-9-D if the serial data rate is less than the radio data rate.
•
After a message is received, a message will not be transmitted during the receive delay time.
This could be used to delay a reply message until other messages have been sent.