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T H E O R Y O F O P E R A T I O N
R F A R C H I T E C T U R E
The CL4490 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, Aerocomm 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 CL4490 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.
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