ICP DAS USA ET-6000 Series User Manual page 159

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Appendix C: Modbus Protocol
Multi Mobus/RTU Master
VxComm Technique
Modbus/RTU
command
protocol
Adjust system settings
The Modbus station number is a very important parameter for ET-6000. It is used to
recognize different Modbus stations. But the ET-6000 does not have any hardware design
such as dip-switch or jump allowing you to set the Modbus station number (or called
NetID). You must set the parameters regarding to Modbus station number by Web page.
System settings include the following:
Net ID (Default = 1):
If the Modbus station number in a Modbus/TCP request (from PC or HMI) matches the
Net ID, the request is passed to the Modbus kernel. Then Modbus kernel program will
then respond and send the internal registers to the Modbus/TCP client (PC or HMI). The
content of all other registers is zero.
Stations per COM port (Default = 10):
This value is used to decide how many Modbus/RTU stations can add on one ET-6000
COM port for control. That also means the value can decide which COM the
Modbus/TCP request will be passed to. The formula is as follows:
COM = station number in Modbus/TCP request /
Example 1:
Stations per COM port = 10
Modbus/TCP requests for station 35
The requests will be passed to COM 3 (35/10 = 3.5)
Example 2:
Stations per COM port = 20
Modbus/TCP requests for station 35
The request will be passed to COM 1 (35/20 = 1.75)
Adjust the COM port settings
ET-6000 User's Manual, 2007, Sep., V1.1,
Internet
Modbus/RTU
Stations per COM port
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