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7.6 Modbus Under Multi-destination IP
As shown in figure 28, if the serial port device (RTU device) is the master station
and the Modbus TCP device (Modbus TCP device) is the slave station, and
multiple network port slave station devices exist simultaneously. In this case, the
serial port server can be used as the client to connect to multiple network port
devices at the same time according to the method introduced in “5.2.2 Client
Connect to Multiple Servers”.
At this point the need to achieve the function is: when instructions sent from the
serial RTU can be sent to more than one network device, the network device
identify whether to send their own through the Slave ID field, only the network
devices corresponding to Slave ID make a response. After the network port reply
is sent to the serial port server, it is converted into RTU instruction and output from
the serial port to the RTU device.
At this point, it is important to note that the two checkmarks shown in figure 37 as
"RS485 bus anti-collision time" and figure 38 as "RS485 instruction reply timeout
time" need to be removed. Otherwise, the above forwarding function cannot be
realized.
Another application method is that although the serial port server connects
multiple network port devices as a Client, the RTU device is not the main station,
but the network port device sends first and the RTU device answers (as the slave
station). At this time, "RS485 bus conflict prevention time" and "RS485 instruction
response timeout time" need to be checked, so that multiple hosts can access a
RTU device at the same time.
8. Registration Pack and Heartbeat Pack
Registration and heartbeat packs are a feature that suitable for communication
between devices and cloud-based software.
8.1 Registration Packet
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