Company Confidential
36
Raveon Technologies Corp.
use hardware flow control. Hardware flow control is enabled with the
ATCH 1
command. Note that the
M8
modem will always indicate the status of its internal
buffer using the CTS signal on the DB-9 serial connector. When CTS is negated,
the internal buffers are more than 80% full. When it is asserted and it is “Clear to
Send”, the buffers are less than 80% full.
6.6. Setting the Over-The-Air Data Rate
The M8 has programmable over-the-air baud rates. The over-the-air rate is
stored in register R2, and is programmed with the
ATR2 x
command, where
x
is
a number corresponding to the rate. The are many possible baud rates, but not
all rates may be used with all radio modem models. Consult the following table.
Over-the-air rate
Radio
Bandwidth
Number of
Modulation
Levels
M8 Modem Models that
support the rates
800bps
(R2=0)
12.5kHz or 25kHz
2
RV-M8-UC-N, RV-M8-UC-W
1200bps
(R2=1)
12.5kHz or 25kHz
2
RV-M8-UC-N, RV-M8-UC-W
2400bps
(R2=2)
12.5kHz or 25kHz
2
RV-M8-UC-N, RV-M8-UC-W
4800bps
(R2=3)
Default setting
12.5kHz or 25kHz
2
RV-M8-UC-N, RV-M8-UC-W
8000bps
(R2=4)
12.5kHz or 25kHz
4
RV-M8-UC-N, RV-M8-UC-W
9600bps
(R2=5)
25kHz
2
RV-M8-UC-W only
19200bps
(R2=6)
25kHz
4
RV-M8-UC-W
(will not work with Radio Type 5)
5142bps
(R2=7
)
12.5kHz or 25kHz
2
RV-M8-UC-N, RV-M8-UC-W, RV-M8-
UC-S
9600bps
(R2=8)
12.5kHz or 25kHz
4
RV-M8-UC-N, RV-M8-UC-W
Changing the over-the-air data rate will change the sensitivity of the receiver.
Higher-data rates require a stronger signal at the receiver to be properly
received. The default over-the-air data rate for
M8
radio modems is 4800 baud
for narrow-band versions, and 9600 baud for wide-band versions.
The maximum over-the-air baud-rate for a narrow-band radio (12.5kHz channel-
spacing) is 9600bps. Due to IF filter limitations, the
M8
does not work as well at
9600 baud as some other rates. Its performance is optimized for 4800 baud 2-
level modulation and 8000 baud 4-level modulation.
The maximum over-the-air baud-rate for a wide-band model (25kHz channel
spacing) is 19200bps. Due to IF filter limitations, it does not work as well at
19200 baud as lower data rates. Its performance is optimized for 9600 baud 2-
level modulation.
RV-M8S-UC (narrow-band version)
Factory default
, set R2 to 3 (4800 baud).
For
high-speed operation
, set R2 to 4 (8000 baud).
