Step 4.3.2. Set Device Point Properties

On the Device tab:

Update Criteria

The update criteria you use determines how the data will be requested.


Select On Change or On Scan for points whose values should be polled by the Modbus TCP/IP driver at regular intervals.


Select On Demand On Scan or On Demand On Change for points whose values should be polled by the Modbus TCP/IP driver at regular intervals while users are viewing them.


Select Unsolicited for points whose value will be sent by the programmable controller as necessary.

Important: The address of the unsolicited data must exactly match the point address.


Enter the point address of the data as follows:


0xxxx or 0xxxxx for Coils

1xxxx or 1xxxxx for Discrete Inputs

3xxxx or 3xxxxx for Input Registers

4xxxx or 4xxxxx for Holding Registers

6yxxxx or 6yxxxxx for General Reference

D4xxxx or D4xxxxx for Holding Registers as Double Precision


where xxxx or xxxxx is the bit number or register number of the point. For example, the address of Holding Register 1 is 40001, and the address of Coil 1 is 00001.


If you are configuring a General Reference point, y is the file number.


Double Precision points in Holding Registers require two Holding Registers per point. The upper register is multiplied by 10000 and the product is added to the lower register to get the resulting value. No more than one Double Precision point may be written in a single write operation. Use DINT or UDINT types for these points.


If you are configuring an Analog point type in Discrete Inputs or Coils, the address entered in this field must be that of the least significant bit of the point. For example, if you configure a 16-bit analog point for Coils 17 through 32, enter 00017 in this field.

When you configure Boolean points in Holding Registers, Input Registers, or General Reference, you must also enter data in the following field:

Bit Offset

Enter the bit offset in the Holding Register, Input Register, or General Reference that defines the point, where 0 is the least significant bit and 15 is the most significant bit.

More information

Step 4.3. Configure Modbus TCP/IP Points.