•
Master to Slave Send time = (9 × 0.04 sec) + (8 retry wait × 0.04 sec) = 1 second
•
Slave to Master 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
4.5 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. (This will directly affect
the battery life of the device.) Adjusting the receive slots changes how often a message can be received. In the battery
power example (default factory settings) the receive slots are 1.3 seconds (receive slots = 4). With the receive slots set to
32, how often a message can be received goes from 1.3 seconds down to 0.16 seconds.
An argument can be made to allow the application accessing the wireless network, in this case the DXM Controller, to
control the retry mechanism. The number of retries can be adjusted in the MultiHop devices by writing Modbus register
6012 to the number of retires desired. The factory default setting is eight.
4.5 DX80 Star Architecture Network Timeouts
The DX80 star network of a Gateway and Nodes can be treated differently with respect to timeout conditions. The DX80
star network is much different from a MultiHop network. In the DX80 network, all Node data is automatically collected at
the Gateway to be read. The DXM Controller does not use the wireless network to access the data, which allows for much
faster messaging and much lower timeout values. For a DXM Controller with an internal DX80 Gateway, set the timeout
value 0.5 seconds. If other Modbus slave devices are connected to the RS-485 lines, the timeout parameter will govern all
communication transactions and must be set to accommodate all devices on the bus.
DXM100 Controller Instruction Manual
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