Company Confidential
27
Raveon Technologies Corp.
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
M8S
contains a 16 bit address, called its Unit Address, and is represented
as a 4 digit hexadecimal number.
M8S
address may be any number between
0000 and FFFF, which is effectively 65,535 different addresses. Every
M8S
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
M8S
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 M8S modem.
The default Address Mask is FFFF, which means all digits will be used. With
these settings, by default all M8s will talk to and hear all other M8S radio
modems.
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,
M8S
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 M8S modems on the channel, but in some other system, they probably
