L-INX User Manual
241
LOYTEC
Version 4.0
LOYTEC electronics GmbH
11.4.5 Modbus Properties
Apart from the common data point properties discussed in Section 6.2.4 the data points of
the Modbus technology have additional properties:
Modbus Device Name
: This property defines the name of the Modbus slave device
which contains the data point.
Modbus Device Address
: This property defines the address of the Modbus slave
device which contains the Modbus data point.
Modbus Register Start Address
: This property defines the address of the Modbus
register.
Modbus Register Type
: This property defines the register type of the data point. Also
the function code, which specifies the register, is displayed. When the Modbus register
type is changed from a read to a write register, also the direction of the data point is
changed.
Modbus Data Type
: This property defines the representation of data in the slave. This
is the data type the Modbus slave uses for the data point internally. This can for
example be float, double, int16 or uint32.
Modbus Multiplier, Exponent and Offset
: This property defines scaling parameters
for the data point. The value of the data point in the LOYTEC device is calculated as
follows:
Value = (Modbu Offset) ∙ Multiplier ∙ 10
Exponent
.
Modbus Swap 16 bit, Swap 32 bit and Swap 64 bit:
This information specifies, if the
order of received Modbus data has to be changed. When Swap 16 bit is set, the two
bytes of a 16 bit word are swapped, if Swap 32 is set, the two words of 32 bit are
swapped, and if Swap 64 bit is set, the two 32 bit words of 64 bit long data are
swapped. Also combinations are possible. This configuration is necessary because the
Modbus slaves can store information in any byte order (the Modbus protocol only
specifies, how 16 bit data is transferred).
Pollgroup
: This property is only available for input data points. It shows the poll
group, the data point is connected to.
11.4.6 Modbus Workflow
This section discusses the workflows for setting up a Modbus environment. Modbus does
not provide a scan function and therefore the network has to be setup offline. This can be
eased by the use of templates. If no templates are available, the data points have to be set up
manually.
Figure 189 describes the workflow for setting up a Modbus network. For using Modbus the
Modbus ports of the LOYTEC device and the Modbus devices have to be configured. The
RS-485 Modbus port must get a Baud rate, the parity is fixed at none and the stop bits are
configured to 2. The Modbus TCP port must get the TCP port number of the slave devices
(see Section 11.3.1). The Modbus devices have to be configured according to the LOYTEC
device‘s port configuration (see Section 11.5.1). When no device template is available for a
Modbus device, it can simply be created by configuring Modbus data points for the device
manually (see Section 11.5.2) and exporting the device template. The exported device
template can then be used to easily add additional Modbus devices with the same data point
configuration (see Section 11.5.3). Also mixing the two methods is possible. When using
the device templates also data points can be added manually. The configuration is then
downloaded to the device and the device is rebooted.
