Steht doch alles ausführlich im XBee-Manual (Ch. 10. "XBee Command
Reference Tables"):
NI
Node Identifier. Set/read a string identifier. The register only accepts
printable ASCII data. In AT Command Mode, a string cannot start with a
space. A carriage return ends the command. A command will automatically
end when maximum bytes for the string have been entered. This string is
returned as part of the ND (Node Discover) command.
This identifier is also used with the DN (Destination Node) command. In
AT command mode, an ASCII comma (0x2C) cannot be used in the NI string
CRE
20-Byte printable
ASCII string
ASCII space
character (0x20)
DN
Destination Node. Resolves an NI (Node Identifier) string to a physical
address (case-sensitive).
The following events occur after the destination node is discovered:
<AT Firmware>
1. DL & DH are set to the extended (64-bit) address of the module with
the matching NI (Node Identifier) string.
2. OK (or ERROR)\r is returned.
3. Command Mode is exited to allow immediate communication
<API Firmware>
1. The 16-bit network and 64-bit extended addresses are returned in an
API
Command Response frame.
If there is no response from a module within (NT * 100) milliseconds or
a parameter is not specified (left blank), the command is terminated and
an “ERROR” message is returned. In the case of an ERROR, Command Mode is
not exited. The radius of the DN command is set by the BH command.
CRE
up to 20-Byte printable
ASCII string
Das Adressieren der einzelnen End-Devices macht man sinnvollerweise im
API-Modus. XBee-Manual, Ch.9 "API Operation".
Dabei baut man sich Datenpakete zusammen, die die entsprechenden
Kommandos/ Payload enthalten.
Wenn Du wirklich ernsthaft mit den XBees arbeiten willst, solltest Du
erstmal das Manual ausführlich studieren. Da kommt man leider nicht drum
herum...