User's Manual

Company Confidential 60 Raveon Technologies Corp.
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ommand. Note that the M7 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.
Packet Size
The over-the-air packet size may be set with the ATTT xx command. Once the
modem receives one full packet of data into via the serial port, it will
automatically key the transmitter and send the data. Factory default is 80 bytes.
Key-On_Data
When serial data is entering the M7’s RS-232 port, the M7 looks for pauses in
the data as indication that it is time to send a packet of data over the air. The
factory default duration of the pause it looks for is 20mS, but the user may
change this to over values using the ATR3 xxx command, where xxx is in
milliseconds.
Busy-Channel Lock Out
If your system operation require the M7 modem to monitor-before-transmit, of if
you do not want the M7 to transmit on a channel that is busy, you can enable
“Busy-Channel-Lockout”, using the ATBC 1 command. ATBC 0 disables BCL,
and thus the modem will transmit whenever it has data to send out. The factory-
default is BCL disabled. Use caution when enabling it, as a CW interferer, PC
with poor shielding, or some other source of RF can stop the modem from
transmitting. The threshold where the M7 senses RF carrier, and determines
that the channel is busy is set by the ATRA command. This is factory calibrated
to an equivalent RF level of approximately -110dBm.
5.4. Data Reception
When the modem receives data over the radio, it checks it for errors, and if it is
error-free, it will send it out the serial port. Again, the serial port may be set to
any baud rate the user wishes, and the radio receiver and transmitter will
continue to operate independently of the baud rate.
When the modem receives a signal, it will assert the CD hardware signal on the
RS-232 serial port if it was configured to do so.
In general, the slower the over-the-air data rate, the easier it is for the modem to
receive the signal, and thus the more communication range the radio will have.
M7 modems have a unique switched-filter along with digital signal processing,
that gives them more range a lower data rates. See Section Error! Reference
source not found. Error! Reference source not found. for more information
about choosing the over-the-air data rate.