CL4790 User Guide
Version 2.0
Americas: +1-800-492-2320 Option 2
Europe: +44-1628-858-940
Hong Kong: +852-2923-0610
www.lairdtech.com/ramp
7
CONN-GUIDE_CL4790
sending the packets until either (1) it receives an acknowledgement, or (2) it has used
all transmit retries. The received packet only sends to the OEM host if and when it is
received free of errors. Note: If Transmit Retries is set to 1 the radio will only attempt
to send the data one time with no retries, the minimum setting for Transmit Retries is
1 and cannot be set to 0.
Broadcast Packets
When sending a broadcast packet, the RF packet sends 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 sends 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 ignores the remaining broadcast attempts. The
received packet is only sent to the OEM host if and when it is received free of errors.
Note: Like Transmit Retries, if Broadcast Attempts is set to 1 the transceiver will send
the data one time with no additional attempts.
Receive Mode
If a transceiver detects a sync pulse, addressed to itself or broadcast on its network, while in Receive Mode, it
will join the Session and begin receiving data. While in Receive Mode, subsequent data of up to 128 bytes
can be received every hop (50 ms). When a transceiver is in Session, its Session Count is decremented by one
every hop. When the Session Count reaches zero, the transceiver exits the Session. In order to continue
receiving data, the transceivers update their Session Count every time data or an RF acknowledge is received.
The SLock0 and SLock1 settings control Session Count as shown below.
Table 1: Session Count Truth Table
Case
Slock0 Slock1 Transceiver Receiving an Addressed Packet
Transceiver Receiving a Broadcast Packet
1
0
0
Radio loads its Current Session Count
with its Session Count Refresh
Radio loads its Current Session Count
with its Session Count Refresh
2
0
1
Radio loads its Current Session Count
with (its Transmit R its Session
Count Refresh)
Radio loads its Current Session Count
with (its broadcast at its
Session Count Refresh)
3*
1
0
Radio loads its Current Session Count
with the remote radio’s Session Count
Refresh
Radio loads its Current Session Count
with the remote radio’s Session Count
Refresh
4
1
1
Radio loads its Current Session Count
with the remote radio’s Current Session
Count
Radio loads its Current Session Count
with the remote radio’s Current Session
Count
* EEPROM Default. This may not be the best setting for all applications. If having issues use Case 4.
Note 1: For Broadcast/Addressed packets, the Session Count for Full Duplex is 2x the value of Session Count in Half Duplex.
Note 2: It is best to have all transceivers with the same Session Count Refresh (EEPROM Address 0xC4) value. Session Count Refresh must not be
set to 0x00.
Case 1
In this case, a radio loads its Session Count with its Session Count Refresh. This is suitable for Half Duplex
communication where immediate response is not expected from the remote radio. Note: The term
“immediate response” refers to the application layer and not the RF acknowledgment.
Case 2
In this case, a radio loads its Session Count with (its Session Count R its Transmit Retries). This case is
suitable for applications where there are high levels of interference and it is likely that transmit retries will be
necessary to maintain reliable communications.
