Specifications
52
The UNITY program comprises several sections, some of them with a transversal role such as PLC system
monitoring or the process sequence.
PLC system monitor the system state (alarms, status, communication...).
Process sequences coordinate the process functions.
In Unity, the program can be represented in two ways:
Using a structural view, b directly related to the PLC application
Using a functional view, b which allows greater readability of the process
Functional view b
A good way to structure a program is by dening functional modules. This method has multiple advantages:
The readability of the program, useful for maintenance or development -
The ability to duplicate a process functional unit easily by export/import -
UNITY program
structuring
Variables
naming rules
The following Tag naming rules is dened before developing the application:
XXX_YYY_ZZZ
XXX: Variable group.
Possible values:
(HMI) : variables exchanged with SCADA/HMI
IO : I/O variables used to control the devices (I/O scanner)
I : Physical input
Q : Physical output
For variables used internally in PLC code (no exchange on I/O, networks, or buses), “XXX_” is omitted.
YYY: Identication of the functional unit to which the device belongs.
ZZZ: Identication of the device type such as pump, motor, valve.
5-Implementation
Unity program implementation