7 OPC UA Types and Instances ToC Previous Next

7.7 WwUnitStateEnumeration ToC Previous Next

This enumeration WwUnitStateEnumeration represents the generalized state of a unit. The enumeration is defined in Table 21.

Table 21 – WwUnitStateEnumeration Items

Name Value Description
OFFLINE 0 The unit is offline.
STANDBY 1 The unit is in standby.
READY 2 The unit is ready to start working.
WORKING 3 The unit is working.
ERROR 4 The unit is not able to work. The cause can be an alarm or error or user intervention. The cause can be an alarm or error or user intervention.

A unit state depends on the unit flags (see 7.9). Even if the unit flags are not provided in the address space they exist internally in the machine. If the device does not support EnergySaving, it is assumed that the variable value is false. Therefore they are always the basis for the state:

  • OFFLINE: !MachineOn

  • STANDBY: MachineOn && (!MachineInitialized || !Calibrated || EnergySaving)

  • READY: MachineOn && MachineInitialized && Calibrated && !EnergySaving &&

    !Error && !RecipeInRun

  • WORKING: MachineOn && MachineInitialized && Calibrated && !EnergySaving &&

    !Error && RecipeInRun

  • ERROR: MachineOn && MachineInitialized && Calibrated && !EnergySaving &&


This is the state diagram of the UnitState:

Note: Since the unit state is an enumeration do not rely on the transitions. Only the logic of the unit flags counts.

readme_files/image013.png Figure 9 – State Machine of the unit state

Its representation in the AddressSpace is defined in Table 22.

Table 22 – WwUnitStateEnumeration Definiton

Attribute Value        
BrowseName WwUnitStateEnumeration        
IsAbstract False        
References Node Class BrowseName DataType TypeDefinition Other
Subtype of the Enumeration type defined in OPC 10000-5          
0:HasProperty Variable 0:EnumValues 0:EnumValueType[] 0:PropertyType  

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