17.2.6 Linking signals
Signals can be linked together to achieve data transfer between several protocols. If a signal source
is defined, all output from that source will be routed to the input of target signal. This way events
polled from a modbus device (e.g., Modbus, IEC 608705, etc.) can be delivered to external station
over a different protocol. A signal source is required if a signal is created on a slave protocol
configuration to link events between protocols.
Example 1
To read a coil state from a Modbus device and transfer it to IEC 608705104 station, following steps
may be taken:
1. Create a Modbus master configuration in Devices sheet.
2. Create a IEC 608705104 slave configuration in Devices sheet.
3. Create a signal on master device to read coil status (function 1).
4. Create a signal on slave device with single point type (data_type = 1).
5. Set
source_device_alias
and
source_signal_alias
fields on slave device signal to match
device_alias
and
ignal_alias
on master device’s coil signal.
Example 2
To write a coil state to a Modbus device on a command from IEC 608705104 station, following
steps may be taken:
1. Follow steps 13 from example 1.
2. Create a signal on slave device with single command type (data_type = 45).
3. Set
source_device_alias
and
source_signal_alias
fields on master configuration coil signal
to match
device_alias
and
signal_alias
on slave device’s command signal. Coil will be written
to a value received by a command.
4. Set
source_device_alias
and
source_signal_alias
fields on command signal to match
device_alias
and
signal_alias
on master device’s coil signal. A command termination signal
will be reported to the station on coil write result.
For additional information regarding configuration of IEC 608705101/103/104
protocols, please refer to ”IEC 607805101/103/104 PID interoperability for WCC
Lite devices”, accordingly.
17.2.7 Mathematical expressions
Signal value might require some recalculation or signal update prior to being sent. Understandably,
existing columns in Excel configuration like
multiply
,
add
,
bit_select
might not be flexible enough.
To overcome these limitations, symbolic mathematical expressions can be configured to do
calculations automatically on every update of a signal.
It should be noted that filling mathematical expression disables other
mathematical scalar operations for a single value such as
multiply
,
add
or
bit_select
. Other functions (primarily between several signals) are still available
such as
operation
.
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