RV-M7 Technical Manual
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. With these settings, by default all M7s will talk to and hear all other M7 radio
modems.
Group Numbers
By default the M7’s Group Number is 0. Group 0 means ignore the group numbering. The Group
Number is set with the ATGP xx command, where xx is the group number. ATGP 0 disables group
numbering and is the default way the M7 radio modem works. If the Group Number is set to any
non-zero number from 1-255, then the group feature is enabled, and the group number will be the
group specified in the ATGP command. When enabled, the M7 will only communicate with other
M7s that have the same Group Number.
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
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
(10 pages)
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