User's Manual

Company Confidential 60 Raveon Technologies Corp.
5.5. Addressing (Packetized Mode only)
Addressing Basics
One of the more powerful aspects of the M7 modem is its addressing scheme.
Incorporating addressing in the modem allows multiple radio systems on the
same frequency to co-exist, and not interfere with each other. Also, some user
application cannot tolerate receiving data that was not intended for it, and by
setting the addresses in the modems properly, the system can be configured to
allow reception of only data intended for the recipient.
If addressing is not needed or desired, it can be turned off so that all modems
receive data from all other modems, and all modems can talk to all other
modems.
Each M7 contains a 16 bit address, called its Unit Address, and is represented as
a 4 digit hexadecimal number. M7 address may be any number between 0000
and FFFF, which is effectively 65,535 different addresses. Every M7 has a Unit
Address programmed into it, as well as the ID of the unit it will send data to. The
Unit Address is programmed with the ATMY 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.