Redfish Ladder Functions

The Redfish Ladder Functions enable interaction between the UniStream PLC and the Redfish server directly from Ladder Logic.
Using these elements, you can trigger Redfish-compliant events, record system data, and modify Redfish Service behavior at runtime.

Notify and Log Event

Use this Ladder function to send a predefined notification and record the event in the system log. All parameters are configured within the action.

	Parameter Name	Purpose
A	Event	Refers to the Redfish Event Struct containing event details.
B	Message ID	Direct Mode: Select a predefined message from the Redfish Message Registry Guide. Environmental - defines messages related to environmental sensors, heating and cooling equipment, or other environmental conditions. Sensor - defines messages used for general events related to Sensor resources.
C	Status	Returns the operation result: 1 - CPU in progress 2 - Panel in progress -1 - Error, Failed to process event -2 - Error, Failed to build event -3 - Error, No SD present -4 - Error, General error -5 - Error, Unsupported property -6 - Error, Invalid event ID

Notify and Log Event Indirect

Use this Ladder function to send and log an event whose details are defined by tag values. This allows event contents to be set dynamically at runtime.

	Parameter Name	Purpose
A	Event	Refers to the Redfish Event Struct.
B	Message ID	Indirect Mode: Assign a numeric data tag containing the event ID from the internal map defining Environmental or Sensor messages.
C	Status	Returns the operation result: 1 - CPU in progress 2 - Panel in progress -1 - Error, Failed to process event -2 - Error, Failed to build event -3 - Error, No SD present -4 - Error, General error -5 - Error, Unsupported property -6 - Error, Invalid event ID

Set Service Property

Use this Ladder element to modify Redfish Service parameters at runtime.

This includes Event Service, Update Service, and Task Service properties.

	Parameter Name	Purpose
A	Service Attribute	Select the Redfish Service Attribute to modify. The available attributes include Event, Update, and Task properties.
B	Service Attribute's Value	Enter a constant or link a tag to modify the selected property's value.
C	Status	Returns the operation result: 0 - Done successfully 1 - CPU in progress 2 - Panel in progress -3 - Failed No SD -4 - Fail General error -5 - Fail Unsupported property

Get All Subscriptions

Use this Ladder element to retrieve all current Redfish Event subscriptions from the PLC.

This function copies the subscription data from the Redfish Event Service to an Indexed Data Table, which you can then read or process using standard Data Table functions.

Parameter Name

Purpose

DTI

Select or create the Data Table that will store the subscription data. The table structure Must match the Redfish Subscription Data Struct

Status

Returns the operation result:
0 - Finished successfully

1 - CPU in progress

2 - Panel in progress

-1 - Panel invalid response

-2 - Error reading xml file

-3 - Invalid xml data

-4 - Write block fail

-5 - Read block fail

-6 - Error opening DT data file

Note: To access the retrieved subscription information, use the Read Row from DTI Ladder element.

Redfish Event Struct

Parameter Name	Type	Purpose
Event Group ID	UINT32	To group related events sharing the same root cause
Message Arg 1	STRING-ASCII	Arg1 - Argument for the message of the event raised
Message Arg 2	STRING-ASCII	Arg2 - Argument for the message of the event raised
Message Arg 3	STRING-ASCII	Arg3 - Argument for the message of the event raised
Message Arg 4	STRING-ASCII	Arg4 - Argument for the message of the event raised
Object ID	STRING-ASCII	The target Redfish Object ID, for example Pump 1 of type 'Redfish Pump Struct' ID member

Redfish Subscription Data Struct

Parameter Name	Type	Purpose
ID	STRING-ASCII	Subscription ID
Destination	STRING-ASCII	Target URI
Context	STRING-ASCII	Client Context String
State	STRING-ASCII	Enabled, Disabled, Suspended
Retry Policy	STRING-ASCII	e.g: TerminateAfterRetries
Message IDs	STRING-ASCII	e.g: Environmental. 1.0.TemperatureAboveUpperCriticalThreshold
Severities	STRING-ASCII	OK, Warning, Critical
Origin Resources	STRING-ASCII	e.g: /redfish/v1/Chassis/Chassis1/Sensors/Sensor1

Redfish Message Registry Guide

Please refer to the Redfish Message Registry Guide by DMTF - DSP2065_2025.3 for the full, detailed documentation of all messages defined in the standard Redfish message registries.

Event ID (internal map)	Message	Severity	Description
Environmental Event Registry
1000	PRESSURE_ABOVE_UPPER_CRITICAL_THRESHOLD	Critical	Indicates that a pressure reading is above the upper critical threshold
1001	Pressure_Above_Upper_Caution_Threshold	Warning	Indicates that a pressure reading is above the upper caution threshold
1002	Pressure_Below_Lower_Critical_Threshold	Critical	Indicates that a pressure reading is below the lower critical threshold
1003	Pressure_Below_Lower_Caution_Threshold	Warning	Indicates that a pressure reading is below the lower caution threshold
1004	Pressure_Normal	OK	Indicates that a pressure reading is now within normal operating range
1005	Humidity_Above_Upper_Critical_Threshold	Critical	Indicates that a humidity reading is above the upper critical threshold
1006	Humidity_Below_Lower_Critical_Threshold	Critical	Indicates that a humidity reading is below the lower critical threshold
1007	Humidity_Normal	OK	Indicates that a humidity reading is now within normal operating range
1008	Flow_Rate_Above_Upper_Caution_Threshold	Warning	Indicates that a flow rate reading is above the upper caution threshold
1009	Flow_Rate_Below_Lower_Critical_Threshold	Critical	Indicates that a flow rate reading is below the lower critical threshold
1010	Flow_Rate_Normal	OK	Indicates that a flow rate reading is now within normal operating range
1011	Fan_Failed	Warning	Indicates that a fan has failed
1012	Fan_Group_Critical	Critical	Indicates that a fan group has a critical status
1013	Fan_Group_Normal	OK	Indicates that a fan group has returned to normal operations
1014	Fan_Group_Warning	Warning	Indicates that a fan group has a warning status
1015	Fan_Inserted	OK	Indicates that a fan was inserted or installed
1016	Fan_Removed	OK	Indicates that a fan was removed
1017	Fan_Restored	OK	Indicates that a fan was repaired or restored to normal operation
1018	Filter_Inserted	OK	Indicates that a filter was inserted or installed
1019	Filter_Removed	OK	Indicates that a filter was removed
1020	Filter_Requires_Service	Warning	Indicates that a filter requires service
1021	Filter_Restored	OK	Indicates that a filter was repaired or restored to normal operation
1022	Filter_Subsystem_Health	OK	Indicates that a filter was repaired or restored to normal operation
1023	Flow_Rate_Above_Lower_Critical_Threshold	Warning	Indicates that a flow rate reading is no longer below the lower critical threshold but is still outside of normal operating range
1024	Flow_Rate_Above_Lower_Fatal_Threshold	Critical	Indicates that a flow rate reading is no longer below the lower fatal threshold but is still outside of normal operating range
1025	Flow_Rate_Above_Upper_Caution_Threshold	Warning	Indicates that a flow rate reading is above the upper caution threshold
1026	Flow_Rate_Above_Upper_Fatal_Threshold	Critical	Indicates that a flow rate reading is above the upper fatal threshold
1027	Flow_Rate_Below_Lower_Caution_Threshold	Warning	Indicates that a flow rate reading is below the lower caution threshold
1028	Flow_Rate_Below_Lower_Fatal_Threshold	Critical	Indicates that a flow rate reading is below the lower fatal threshold
1029	Flow_Rate_Below_Upper_Critical_Threshold	Warning	Indicates that a flow rate reading is no longer above the upper critical threshold but is still outside of normal operating range
1030	Flow_Rate_Below_Upper_Fatal_Threshold	Critical	Indicates that a flow rate reading is no longer above the upper fatal threshold but is still outside of normal operating range
1031	Flow_Rate_Critical	Critical	Indicates that a flow rate reading exceeds an internal critical level
1032	Flow_Rate_Fatal	Critical	Indicates that a flow rate reading exceeds an internal fatal level or flow rate reading is zero (0)
1033	Flow_Rate_No_Longer_Critical	Warning	Indicates that a flow rate reading no longer exceeds an internal critical level but still exceeds an internal warning level
1034	Flow_Rate_No_Longer_Fatal	Critical	Indicates that a flow rate reading is no longer exceeds an internal fatal level but is still exceeds an internal critical level
1035	Flow_Rate_Warning	Warning	Indicates that a flow rate reading is now within normal operating range
1036	Fluid_Level_Above_Lower_Critical_Threshold	Warning	Indicates that a fluid level reading is no longer below the lower critical threshold but is still outside of normal operating range
1037	Fluid_Level_Above_Lower_Fatal_Threshold	Critical	Indicates that a fluid level reading is no longer below the lower fatal threshold but is still outside of normal operating range
1038	Fluid_Level_Above_Upper_Caution_Threshold	Warning	Indicates that a fluid level reading is above the upper caution threshold
1039	Fluid_Level_Above_Upper_Critical_Threshold	Critical	Indicates that a fluid level reading is above the upper critical threshold
1040	Fluid_Level_Above_Upper_Fatal_Threshold	Critical	Indicates that a fluid level reading is above the upper fatal threshold
1041	Fluid_Level_Below_Lower_Caution_Threshold	Warning	Indicates that a fluid level reading is below the lower caution threshold
1042	Fluid_Level_Below_Lower_Critical_Threshold	Critical	Indicates that a fluid level reading is below the lower critical threshold
1043	Fluid_Level_Below_Lower_Fatal_Threshold	Critical	Indicates that a fluid level reading is below the lower fatal threshold
1044	Fluid_Level_Below_Upper_Critical_Threshold	Warning	Indicates that a fluid level reading is no longer above the upper critical threshold but is still outside of normal operating range
1045	Fluid_Level_Below_Upper_Fatal_Threshold	Critical	Indicates that a fluid level reading is no longer above the upper fatal threshold but is still outside of normal operating range
1046	Fluid_Level_Critical	Critical	Indicates that a fluid level reading violates an internal critical level
1047	Fluid_Level_No_Longer_Critical	Warning	Indicates that a fluid level reading no longer violates an internal critical level but still violates an internal warning level
1048	Fluid_Level_Normal	OK	Indicates that a fluid level reading is now within normal operating range
1049	Fluid_Level_Warning	Warning	Indicates that a fluid level reading violates an internal warning level
1050	Fluid_Quality_Critical	Critical	Indicates that a fluid quality reading exceeds an internal critical level
1051	Fluid_Quality_No_Longer_Critical	Warning	Indicates that a fluid quality reading no longer exceeds an internal critical level but still exceeds an internal warning level
1052	Fluid_Quality_Normal	OK	Indicates that a fluid quality reading is now within normal operating range
1053	Fluid_Quality_Warning	Warning	Indicates that a fluid quality reading exceeds an internal warning level
1054	Humidity_Above_Lower_Critical_Threshold	Warning	Indicates that a humidity reading is no longer below the lower critical threshold but is still outside of normal operating range
1055	Humidity_Above_Upper_Caution_Threshold	Warning	Indicates that a humidity reading is above the upper caution threshold
1056	Humidity_Below_Lower_Caution_Threshold	Warning	Indicates that a humidity reading is below the lower caution threshold
1057	Humidity_Below_Upper_Critical_Threshold	Warning	Indicates that a humidity reading is no longer above the upper critical threshold but is still outside of normal operating range
1058	Leak_Detected_Critical	Critical	Indicates that a leak detector is in a critical state
1059	Leak_Detected_Normal	OK	Indicates that a leak detector is within normal operating range
1060	Leak_Detected_Warning	Warning	Indicates that a leak detector is in a warning state
1061	Leak_Detected_Connected
1062	Leak_Detected_Disconnected
1063	Leak_Detected_Failure
1064	Leak_Detected_Restored
1065	Pressure_Above_Lower_Critical_Threshold	Warning	Indicates that a pressure reading is no longer below the lower critical threshold but is still outside of normal operating range
1066	Pressure_Above_Lower_Fatal_Threshold	Critical	Indicates that a pressure reading is no longer below the lower fatal threshold but is still outside of normal operating range
1067	Pressure_Above_Upper_Fatal_Threshold	Critical	Indicates that a pressure reading is above the upper fatal threshold
1068	Pressure_Below_Lower_Fatal_Threshold	Critical	Indicates that a pressure reading is below the lower fatal threshold
1069	Pressure_Below_Upper_Critical_Threshold	Warning	Indicates that a pressure reading is no longer above the upper critical threshold but is still outside of normal operating range
1070	Pressure_Below_Upper_Fatal_Threshold	Critical	Indicates that a pressure reading is no longer above the upper fatal threshold but is still outside of normal operating range
1071	Pressure_Critical	Critical	Indicates that a pressure reading exceeds an internal critical level
1072	Pressure_No_Longer_Critical	Warning	Indicates that a pressure reading no longer violates an internal critical level but still violates an internal warning level
1073	Pressure_Warning	Warning	Indicates that a pressure reading exceeds an internal warning level
1074	Primary_Coolant_Connector_Subsystem_Health
1075	Pump_Failed	Warning	Indicates that a pump has failed
1076	Pump_Inserted	OK	Indicates that a pump was inserted or installed
1077	Pump_Removed	OK	Indicates that a pump was removed
1078	Pump_Restored	OK	Indicates that a pump was repaired or restored to normal operation
1079	Pump_Subsystem_Health
1080	Reservoir_Subsystem_Health
1081	Secondary_Coolant_Connector_Subsystem_Health
1082	Temperature_Above_Lower_Critical_Threshold	Warning	Indicates that a temperature reading is no longer below the lower critical threshold but is still outside of normal operating range
1083	Temperature_Above_Lower_Fatal_Threshold	Critical	Indicates that a temperature reading is no longer below the lower fatal threshold but is still outside of normal operating range
1084	Temperature_Above_Upper_Caution_Threshold	Warning	Indicates that a temperature reading is above the upper caution threshold
1085	Temperature_Above_Upper_Critical_Threshold	Critical	Indicates that a temperature reading is above the upper critical threshold
1086	Temperature_Above_Upper_Fatal_Threshold	Critical	Indicates that a temperature reading is above the upper fatal threshold
1087	Temperature_Below_Lower_Caution_Threshold	Warning	Indicates that a temperature reading is below the lower caution threshold
1088	Temperature_Below_Lower_Critical_Threshold	Critical	Indicates that a temperature reading is below the lower critical threshold
1089	Temperature_Below_Lower_Fatal_Threshold	Critical	Indicates that a temperature reading is below the lower fatal threshold
1090	Temperature_Below_Upper_Critical_Threshold	Warning	Indicates that a temperature reading is no longer above the upper critical threshold but is still outside of normal operating range
1091	Temperature_Below_Upper_Fatal_Threshold	Critical	Indicates that a temperature reading is no longer above the upper fatal threshold but is still outside of normal operating range
1092	Temperature_Critical	Critical	Indicates that a temperature reading exceeds an internal critical level
1093	Temperature_No_Longer_Critical	Warning	Indicates that a temperature reading no longer exceeds an internal critical level but still exceeds an internal warning level
1094	Temperature_Normal	OK	Indicates that a temperature reading is now within normal operating range
1095	Temperature_Warning	Warning	Indicates that a temperature reading exceeds an internal warning level
1096	Valve_Closed
1097	Valve_Opened
1098	Valve_Position_Changed
1099	Valve_Unable_To_Reach_Set_Point
1100	Valve_Unable_To_Reach_Set_Point_Percent
Sensor Event Registry
5000	Invalid_Sensor_Reading	Warning	Indicates that the service received an invalid reading from a sensor
5001	Reading_Above Lower_Critical_Threshold	Warning	Indicates that a sensor reading is no longer below the lower critical threshold but is still outside of normal operating range
5002	Reading_Above Lower_Fatal_Threshold	Critical	Indicates that a sensor reading is no longer below the lower fatal threshold but is still outside of normal operating range
5003	Reading_Above Upper_Caution_Threshold	Warning	Indicates that a sensor reading is above the upper caution threshold
5004	Reading_Above Upper_Critical_Threshold	Critical	Indicates that a sensor reading is above the upper critical threshold
5005	Reading_Above Upper_Fatal_Threshold	Critical	Indicates that a sensor reading is above the upper fatal threshold
5006	Reading_Below_Lower_Caution_Threshold	Warning	Indicates that a sensor reading is below the lower caution threshold
5007	Reading_Below_Lower_Critical_Threshold	Critical	Indicates that a sensor reading is below the lower critical threshold
5008	Reading_Below_Lower_Fatal_Threshold	Critical	Indicates that a sensor reading is below the lower fatal threshold
5009	Reading_Below_Upper_Critical_Threshold	Warning	Indicates that a sensor reading is no longer above the upper critical threshold but is still outside of normal operating range
5010	Reading_Below_Upper_Fatal_Threshold	Critical	Indicates that a sensor reading is no longer above the upper fatal threshold but is still outside of normal operating range
5011	Reading_Critical	Critical	Indicates that a sensor reading exceeds an internal critical level
5012	Reading_No_Longer_Critical	Warning	Indicates that a sensor reading no longer exceeds an internal critical level but still exceeds an internal warning level
5013	Reading_Warning	Warning	Indicates that a sensor reading exceeds an internal warning level
5014	Sensor_Connected	OK	Indicates that an external sensor was connected
5015	Sensor_Disconnected	Warning	Indicates that an external sensor was disconnected
5016	Sensor_Failure	Warning	Indicates that the service cannot communicate with a sensor or detected a failure
5017	Sensor_Reading_Normal_Range	OK	Indicates that a sensor reading is now within normal operating range
5018	Sensor_Restored	OK	Indicates that a sensor was repaired or communications were restored. It may also indicate that the service is receiving valid data from a sensor