User manual
4
T H E O R Y O F O P E R A T I O N 4
R F A R C
H I T E C T U R
E
The
NL900PRO utilizes a Server-Client
network where all Clients synchronize
their hopping to the Server. The
Server transmits a
beacon during
the first 1 ms of
every hop (20 ms).
The Client transceivers listen for this
beacon and upon hearing it assert their
In Range Low
and synchronize
their hopping with
the Server.
Each network should consist of only one Server and there should never be
two servers on the same RF
Channel number
in the
same coverage
area as the interference between the two servers will severely
hinder RF
communications. For those applications
requiring collocated
servers, Raveon Technologies
recommends using the Sync-to-Channel feature which is further explained in the Sync-to-Channel
Appendix.
M O D E S O F O P
E R A T I O N
The NL900PRO has three
different operating modes;
Receive,
Transmit, & Command Mode. If the
transceiver is not communicating with another radio,
it will be in Receive Mode actively listening for a
beacon from the
Server.
If the
Client determines that the beacon is
from a server operating on the
same
RF Channel and
System
ID, it
will respond by
asserting In Range Low. A
transceiver will enter Transmit or
Command
mode when
the OEM Host sends data over the serial interface.
T R A N S M I T M O D E
All packets sent over the RF are either Addressed or
Broadcast packets. Broadcast and Addressed delivery
can be controlled dynamically with the API Control
byte and corresponding on-the-fly commands. To
prohibit
transceivers from receiving broadcast packets, Unicast only can be
enabled.
A D D R E S S E D P A C K E T S
When sending an addressed
packet, the
RF packet is sent only to the receiver specified in destination
address.
To increase the odds of successful delivery, Transmit retries are utilized. Transparent to the OEM
Host; the sending radio will send
the RF
packet to the intended
receiver. If
the receiver receives the packet
free
of errors, it
will
return an RF
acknowledge within
the same 20 ms
hop.
If a
receive
acknowledgement
is not received, the radio will use a transmit retry to resend the
packet. The radio will continue sending the
packet until either (1) an acknowledgement is received or (2) all transmit
retries
have been used. The
received packet will only be sent to the OEM Host if and when
it is received
free of errors.
B R O A D C A S T P A C K E T S
When sending a broadcast packet,
the RF packet is sent out to every
eligible transceiver on the network. To
increase the
odds
of
successful delivery, Broadcast attempts are
utilized.
Transparent
to
the OEM Host, the
sending radio will
send the RF packet to the
intended receiver(s).
Unlike transmit retries, all broadcast attempts are
used; regardless of when the RF packet is actually
received and without RF acknowledgements. If the packet is received on
the first attempt, the receiver will
ignore the remaining broadcast attempts. The received packet will only be
sent to
the OEM Host if and
when it is received
free of errors.