The Modbus TCP/IP driver can read and write (client mode) data points and registers from server devices. It can also provide data points and registers as a server device.

Each Modbus server can provide four different types of registers.

For the registers different read and write functions are used.

The name of the Modbus driver is: mbtcp
The routing address of the first driver is 860
The data points file of the first Modbus driver is: mbtcp1.txt
The configuration file for global settings of the first Modbus driver: mbtcp1.cfg

For the Modbus driver as well as all other gateway drivers the following definitions are valid:

Addresses are defined as follows:

<ip> <server/unit_ID> <register> <no>[.<bit>]

Communication state with Modbus server: „<server> failure“

While following definition is valid:

The address of the Coil-Register 120 of server „192.168.1.1 2“ is defined in the data point file mbtcpX.txt as follows:

[M 192.168.1.1 2 coil 120]

In order to inform the driver how to handle the stored information the format for each data point must be defined.:

format = <format> [S:<swap>] [F:<fact>] [O:<ofs>] [M:<mode>]

While <format> can be as follows:

For Coil- or status registers no format is required.

32bit-formats require more than one register, Missing registers are built from successing registers. Those registers are not available for following registers anymore!

For the correct interpretation of data points some devices require an inverted byte order of the register content. This can be solved by using the parameter <swap>.

When using the format BIT for single bits of holding or input registers the <swap> parameter will be ignored.

While <swap> can have following values:

The parameter „F:“ contains a factor. The value received will be divided by the value in „F:“ factor.

In order to enable integer values to contain decimal places the integer value is divided by the factor F:. A value can be multiplied by 10 on the sender's side and divided again on receiver's side by 10. E.g. a temperature of 20.5 °C will be transferred as „205“. To ensure a correct display of the temperature on receiver's side the format parameter „F:10.0“ will divide the value by 10 and the correct value of 20.5 will be displayed again.

Default value for factor is 1

Parameter „O“ represents an offset. This offset is added to the data point's value.

Parameter „M“ allows to link additional modes with the data point.

M: can have following values:

Typical data point definitions for remote data point can be:

[M 192.168.1.1 2 status 5]
 name = digital operation mode statement
 query = pe
 format = BIT

[S 192.168.1.1 2 coil 10]
 name = digital given value   
 query = pe
 format = BIT
 writecache = yes

[M 192.168.1.1 2 input 10.3]
 name = digital operation mode statement
 query = pe
 format = BIT

[S 192.168.1.1 2 holding 11.5]
 name = digital given value
 query = pe
 format = BIT
 writecache = yes

[M 192.168.1.1 2 holding 15]
 name = multistate message z.B. 0, 1, 2 for Off, On, Auto
 query = pe
 format = UINT16

[S 192.168.1.1 2 holding 16]
 name = multistate given value e.g. level switch 0, 1, 2 for Off, On, Auto
 query = pe
 format = UINT16
 writecache = yes

[X 192.168.1.1 2 input 17]
 name = Temperature value (Register 17+18)
 query = pe
 format = FLOAT32

[Y 192.168.1.1 2 holding 17]
 name = Temperature given value, one decimal place
 query = pe
 format = SINT16 F:10
 writecache = yes

Typical local data points can be:

[S 0.0.0.0 2 status 5]
 name = digital operation mode statement
 query = pe
 format = BIT
 writecache = yes

[M 0.0.0.0 2 coil 10]
 name = digital given value
 query = pe
 format = BIT

[S 0.0.0.0 2 input 10.3]
 name = digital operation mode statement
 query = pe
 format = BIT
 writecache = yes

[M 0.0.0.0 2 holding 11.5]
 name = digital given value
 query = pe
 format = BIT

[S 0.0.0.0 2 holding 15]
 name = multistate message e.g. level switch 0, 1, 2 for Off, On, Auto

 query = pe
 format = UINT16
 writecache = yes

[M 0.0.0.0 2 holding 16]
 name = multistate message e.g. level switch 0,1,2 for Off, On, Auto
 query = pe
 format = UINT16

[Y 0.0.0.0 2 input 17]
 name = Temperature value (Register 17+18)
 query = pe
 format = FLOAT32
 writecache = yes

[X 0.0.0.0 2 holding 17]
 name = Temperature given value, one decimal place
 query = pe
 format = SINT16 F:10