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Connecting Multiple Modbus Devices to a Single Serial Port Using Lookout

Primary Software: Lookout
Primary Software Version: 6.0.2
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
I have several Modbus devices connected to an intermediate device which exposes a single modbus serial port. How can I talk to all of these modbus devices using Lookout?

Solution:
There are two main steps required to achieve this functionality.

1. Create a Sequencer object which will eventually be used to turn on and off Lookout Modbus objects by cycling through them. There should be one sequencer state per Modbus device. This is necessary since only one Modbus object can be actively polling at a given time on a single serial resource.


2. Create one Modbus object for each Modbus device, and set the Address parameter in the Revise Modbus Secondary configuration dialog box to the Slave ID of the corresponding device. In the configuration dialog box for each modbus object, set the Poll parameter to a distinct state defined in the Sequencer object.

Example:
Suppose there are three Modbus devices and three Modbus objects in Lookout configured as described along with a Sequencer object named Sequencer, with states A, B, and C defined. To implement the desired functionality, the Poll parameter in the Lookout Modbus configuration dialog for the three Modbus objects can be set to Sequencer.A, Sequencer.B, and Sequencer.C, respectively.

Refer to the Lookout Help for further details on configuring Modbus and Sequencer objects.

Related Links:
KnowledgeBase 2ALCKQ6Q: Can I Simulate a Modbus PLC in Lookout?

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Report Date: 03/15/2007
Last Updated: 03/27/2007
Document ID: 47EBSB4B

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