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Acquire™ is a trademark of Ambrit Ltd

Setting up a Modbus Server

This is an optional feature and will only be available if it has been licensed in the key file.

Acquire must be in Config mode to perform these steps.

1. Select ‘Modbus Server…’ from the ‘Config’ menu

The Modbus Servers list will be displayed:

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2. Click the ‘Add’ button

The Modbus Servers settings screen will be displayed:

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3. Enter the fields as follows:

Server Name This is the name used to identify the Modbus server.
Connection Type The Modbus server can be set to connect via TCP or Serial. The Connection Type will affect which parameters appear on this screen.

Acquire always uses the Modbus TCP protocol for TCP connections and Modbus RTU protocol for serial connections.

IP Address (TCP only) This is the IP address that the Modbus server will respond on. The IP address entered must be one of the server’s own allocated IP addresses.
TCP Address (TCP port only) This is the TCP port that the Modbus server will use. The default port is 502.
No of Connections (TCP only) This is the number of external machines that can connect to this Modbus server.
Comm Port (Serial only) This is the serial port that the Modbus server is connected to
Baud Rate (Serial only) This is the baud rate that the connection will use.
Data Bits (Serial only) This is the data bits that the connection will use. The default value is 8.
Stop Bits (Serial only) This is the stop bits that the connection will use. The default value is 1.
Parity (Serial only) This is the parity that the connection will use. The default value is None.
Stop Bits (Serial only) This is the stop bits that the connection will use. The default value is 1.
Slave ID This is the slave address that the Modbus server will use. The default value is 1.
Timeout This is the time in seconds that Acquire will wait for an incoming request. If a request does not occur in this time, the server will disconnect the connection.
Skip Blanks A standard Modbus poll scans consecutive addresses. Select ‘Skip Blanks’ to allow a Modbus poll to request values over non-consecutive Modbus addresses.
Pass Through This checkbox passes through the flow computer connection straight through to the Modbus server. Once this option has been selected choose the flow computer to pass through.

When using pass through, there is no need to define the Modbus map as it uses the connected flow computer’s Modbus map. eg polling for Modbus address 7000 on the Modbus server will retrieve the value for address 7000 in the flow computer.

4. Click the ‘Modbus Map’ tab

The Modbus Map screen will be displayed:

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5. Select the flow computer from the ‘Flow Computer’ popup menu

6. Enter the Modbus address or field name into the ‘Search’ field

7. Click the ‘Go’ button

A list of matching fields in the flow computer’s Modbus map will be displayed:

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7. Click the ‘Add’ button

The field will be added to the Modbus Server’s Modbus map.

The field can also be added by dragging it into the list.

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When the Modbus Server receives a request for a field from a Modbus client, Acquire will request the corresponding field from the flow computer and then pass the value back to the Modbus client. Any field type conversions are handled automatically.

In the above example, polling the Modbus Server for Server Address at address ”1″ will return the value from Flow Computer at address ”7101″.

Data can be written back to the flow computer from the Modbus client in exactly the same way.

8. Highlight the address in the Modbus Server map list

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9. Click the ‘Edit’ button

The Modbus Server Field window will be displayed:

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The Modbus Address and the Date Type fields can be changed on this screen.

10. Click the ‘OK’ button

This will return to the Modbus Map screen:

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11. Click the ‘OK’ button

This will activate the changes to the Modbus Server.

Tip: Click the ‘Apply’ button to activate the changes without closing the screen.