User's Manual

Company Confidential 17 Raveon Technologies
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-UC 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-UC to ignore the address,
and receive every transmission. The disadvantage to this method is the
adjacent-system problem. If there is another M7-UC system on the same
channel, all modems with the 0000 mask will receive them also.
Most users who do not use individual modem addressing, choose to set a
global system address, and have all modems in their system use the same
Unit ID and same destination address.
Broadcast Transmissions
The double FF is used to identify a broadcast packet. A transmission with a
two digit FF in the first two positions of the destination ID, or in the last two
positions of the destination ID, will be interpreted as a broadcast, and any
modem with an ID that matches the two non-FF digits will receive the data.
For example, sending data with a destination ID of 12FF will be received by
any modem with a unit ID 1200 through 12FF. Sending data with a
destination ID of FF34 will be received by any modem with a unit ID of 0034
through FF34.
The Address Mask
The reason to use hexadecimal digits to represent the unit address, is that
along with the Unit Address programmed into the M7-UC, there is an
“Address Mask” programmed into it. The default mask is FFFF. The address
mask is also used to determine if a particular data transmission should be
received by the modem. For most applications, where one modem talks to
one modem, or where all modems in the system communicate with all other
modems in the system, the Address Mask should stay set to FFFF.
Only in systems where some modems should only talk to certain other
modems, might you want to change the address mask. Whenever data is
received over the air, the Destination Address of the transmission is logically
“ANDed” with the Address Mask in the receiving modem. This is the Effective
Destination Address. The receiving M7-UC also ANDs its own Unit Address
with its Address Mask. The result is the Effective Unit Address. The Effective