Calculating The Communications Timeout For Battery-Powered Multihop Radios; Calculating The Communication Timeout For 10-30 Vdc Multihop Radios; Adjusting The Receive Slots And Retry Count Parameters; Calculating The Communication Timeout For A Dx80 Star Network - Banner DXM1200-Bx Instruction Manual

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7.4.2. Calculating the Communications Timeout for Battery-Powered MultiHop
Radios
Battery-powered MultiHop radios are configured to run efficiently to maximize battery life. By optimizing battery life, the allowed communications
window to receive messages is slow (once per 1.3 seconds) and sending message rates are standard (once per 0.04 seconds).
A MultiHop device is set from the factory with the retry parameter of 8. This means that under worst-case conditions, a message is sent from the
DXM1200 to an end device a total of nine times (one initial message and eight retry messages). The end device sends the acknowledgment
message back to the DXM1200 a maximum of nine times (one initial message and eight retries). A single Modbus transaction may send up to
two messages + 16 retry messages before the transaction is complete. In addition, the radios randomly wait up to one time period before retrans-
mitting a retry message. So to allow for the random wait time, add one extra time period for each in-between time of retries.
To calculate the communication timeout parameter for a client to a server radio (no repeaters):
• Client to Server Send time = (9 × 1.3 sec) + (8 retry wait × 1.3 sec) = 22 seconds
• Server to Client Send time = (9 × 0.04 sec) + (8 retry wait × 0.04 sec) = 1 second
• Total Send/Receive time = 23 seconds
• Minimum Timeout period = 23 seconds
If the link quality of the network is poor, the maximum transfer times may happen. Set the timeout parameter to accommodate the maximum
number of retries that may happen in your application.
When MultiHop repeaters are added to the wireless network, each additional level of hierarchical network increases the required timeout period.
Since MultiHop repeaters are running at the highest communications rate, the overall effect is not as great.
• Client to Repeater Send time = (9 × 0.04 sec) + (8 retry wait × 0.04 sec) = 1 second
• Repeater to Client Send time = (9 × 0.04 sec) + (8 retry wait × 0.04 sec) = 1 second
• Additional Timeout period for a repeater = 2 seconds
Using the timeout calculation above of 23 seconds, if a repeater is added to the network the timeout should be set to 25 seconds. For each addi-
tional MultiHop repeater device creating another level of network hierarchy, add an additional two seconds to the timeout period.
7.4.3. Calculating the Communication Timeout for 10–30 VDC MultiHop Radios
Line-powered (10–30 V DC) MultiHop devices operate at the maximum communication rate, resulting in a much lower timeout parameter setting.
For each repeater added to the network, increase the timeout parameter 2 seconds.
For a client radio to a 10–30 V DC powered server radio (no repeaters):
• Client to Server Send time = (9 × 0.04 sec) + (8 retry wait × 0.04 sec) = 1 second
• Server to Client Send time = (9 ×* 0.04 sec) + (8 retry wait × 0.04 sec) = 1 second
• Total send/receive time = 2 seconds
• Minimum timeout period = 2 seconds

7.4.4. Adjusting the Receive Slots and Retry Count Parameters

The number of receive slots governs how often a MultiHop device can communicate on the wireless network.
Battery-powered devices typically have DIP switches that allow the user to set the number of receive slots, which directly affects the battery life
of the radio. Adjusting the receive slots changes how often a message can be received. By default, the receive slots are set to 4 (every 1.3
seconds). When the receive slots are set to 32, the radio listens for an incoming message every 0.16 seconds.
Users may also leave the retry mechanism to the application that is accessing the wireless network, in this case the DXM1200. Adjust the number
of retries in the MultiHop devices by writing the number of retries desired to Modbus register 6012. The factory default setting is 8.

7.4.5. Calculating the Communication Timeout for a DX80 Star Network

In the DX80 network, all Node data is automatically collected at the Gateway to be read. The DXM1200 does not use the wireless network to
access the data, which allows for much faster messaging and much lower timeout values.
For a DXM1200 with an internal DX80 Gateway, set the timeout value 0.5 seconds. If other Modbus devices are connected to the RS-485 lines,
the timeout parameter governs all communication transactions and must be set to accommodate all devices on the bus.

7.5. Modbus TCP Client

The DXM1200 can operate as a Modbus TCP client on Ethernet. Users may define up to five socket connections for Modbus TCP server devices
to read Modbus register data over Ethernet. Use the DXM Configuration Software to define and configure Modbus TCP client communications
with other Modbus TCP servers.
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