User's Manual

Company Confidential 60 Raveon Technologies Corp.
Unit Address is programmed with the A
TMY xxxx command, and the Unit
Address of the destination modem (the Destination Address) is configured with
the ATDT xxxx command.
The defaults UNIT ID in al M7 modems is 1234, and 1234 is the default for the
destination ID. An Address Mask is used to select which digits of the address will
be used to determine if a particular reception was intended for the M7 modem.
The default Address Mask is FFFF, which means all digits will be used.
Hexadecimal Numbers
For those not familiar with hexadecimal numbers, a hexadecimal digit represents
a 4-bit binary pattern. There are 16 possible values
(0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,and F). These 16 values represent 4 bits of
information, thus 4 hexadecimal digits can represent 16 bits of information. The
hexadecimal numbers represent 4 bit data in the following way:
Hexadecimal Table
Hex # Binary Hex # Binary Hex # Binary Hex # Binary
0 0000 5 0100 8 1000 C 1100
1 0001 6 0101 9 1001 D 1101
2 0010 7 0110 A 1010 E 1110
3 0011 8 0111 B 1011 F 1111
When communicating over the air, M7 modems transmit their Unit Address and
the Destination Address along with the data. Receiving modems check the
received Destination Address, and see if it matches their Unit Address. If it does
match, the receiving modem outputs the data it received via its serial port. If it
does not match, the receiving modem discards the data, and does not send it out
the serial port.
Setting A System-Wide Address
If individual addressing is not needed in your system, there are two ways to
ensure it is not used. One way is to set all modems in the system with the same
Unit Address and destination address. From the factory, these are both set to
1234, and thus, all modems can communicate with all other modems, using the
address 1234. The advantage of using this system-wide address, is that if there
are other M7 modems on the channel, but in some other system, they probably
will not have the same Unit Address, and thus will not interfere with your system.
To reduce the possibility of data cross-talk, the system implementer may wish to
use a different system-wide address for the Unit Address instead of 1234. There
are over 65,000 addresses available.
An alternate way to disable addressing altogether, is set the Address Mask to
0000 (ATMK 0000 command). This tells the M7 to ignore the address, and
receive every transmission. The disadvantage to this method is the adjacent-
system problem. If there is another M7 system on the same channel, all
modems with the 0000 mask will receive them also.