Epec Programming and Libraries Manual
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Supported platforms: CODESYS 3.5, CODESYS 3.5 SAFETY

 

S_ValueDiagnostic (FB)

Description

This function block monitors that the input signal value is between given error limits.

 

This function block can diagnose any numeric value (quantity).

 

Initialization

Init method is used to initialize the necessary static calculation parameters for the function block instance.

The method shall be called at least once before the actual function block can be called, i.e. at the application initialization phase.

The method checks the validity of input parameters. However, none of the function block outputs are affected by the initialization.

 

A parameter error is diagnosed if:

• Init method is not called before the main FB call OR

• i_pEventCode = 0 OR

• S_i_HighErrorLimit ≤ S_i_LowErrorLimit

 

 

Initialization parameters

Parameter

Data type

Unit

Range

Description

S_i_HighErrorLimit

SAFEDINT

-

> S_i_LowErrorLimit

High error limit for value

S_i_LowErrorLimit

SAFEDINT

-

< S_i_HighErrorLimit

Low error limit for value.

S_i_EnableHighError

SAFEBOOL

-

-

Enable high error diagnostic.

S_i_EnableLowError

SAFEBOOL

-

-

Enable low error diagnostic.

S_i_DiagnosticDelay

SAFEUINT

ms

-

Delay time for diagnostics.

S_i_SafeOutputValue

SAFEDINT

-

-

Safe output value in case of error

i_pEventCode

POINTER TO EventCode

-

≠ 0

Pointer to application variable which is type EventCode. Used with POUs that handle signal data.

 

Initialization method return value

TRUE: All initialization parameters ok.

FALSE: Error in initialization parameter(s).

 

 

Operation

This POU monitors that input value S_i_Value is between given error limits. The monitoring is active when the input value i_Enable is true, input parameters are valid and the corresponding error monitoring is enabled.

 

The high error is diagnosed if the high error diagnostic is enabled and input value > high error limit for diagnostic delay time.

The low error is diagnosed if the low error diagnostic is enabled and input value < low error limit for diagnostic delay time.

 

The block sets o_Status.OutputValid state TRUE if signal is between given error limits and operation is enabled, i.e. i_Enable is TRUE

Operation in fault situations

If if input value is out of given limits continuously over S_i_DiagnosticDelay time, then

• S_o_Output is set to given safe value,

• Status o_Status.OutputValid is set FALSE,

• The corresponding Error bit in o_Status variable is set TRUE, and

• The corresponding EventID is set to i_pEventCode

 

All function block statuses, including errors are reset on rising edge of i_Enable.

 

Inputs

Input variable name

Data type

Range

Description

i_Enable

BOOL

-

Enable POU operation

S_i_Value

SAFEDINT

-

Monitored value

Outputs

Output variable name

Data type

Range

Description

S_o_Output

SAFEDINT

-

Monitored output value.

o_Status

Status

-

Monitored signal status.

Error diagnostic

See Diagnostic Interface library description of error status and event code functionality.

 

Conditions

S_o_Output value

o_Status. OutputValid

o_Status error status

Event code FunctionID

Event code EventID

i_Enable TRUE

AND

init parameter error AND

 i_pEventCode valid

S_i_Safe OutputValue

FALSE

ParameterError

VALUE_ DIAGNOSTIC

PARAMETER_ERROR

i_Enable TRUE

AND

init parameter error AND
i_pEventCode NULL

S_i_Safe OutputValue

FALSE

ParameterError

-

-

i_Enable rises

AND

 init parameters ok AND

S_i_Value between error limits

S_i_Value

TRUE

-

NO_FUNC

NO_ERROR

i_Enable TRUE

AND

 init parameters ok AND

S_i_EnableHighError TRUE

AND

S_i_Value >  S_i_HighErrorLimit

S_i_Safe OutputValue

FALSE

ValueHighError

VALUE_ DIAGNOSTIC

INPUT_TOO_HIGH

i_Enable TRUE

AND

 init parameters ok AND

S_i_EnableLowError TRUE

AND

S_i_Value <  S_i_LowErrorLimit

S_i_Safe OutputValue

FALSE

ValueLowError

VALUE_ DIAGNOSTIC

INPUT_TOO_LOW

 

Example code

MultiTool Creator generated code do not include this function block.

 

Location of the POU instance depends on the application: Non-safe inputs are handled in non-safe context, safe inputs are handled in safe context. The example code applies to both.

 

Non-safe Definitions:

 

 

EngineTempValid: ValidateAI;                 // temperature validation FB, not included to this example.

EngineTempValidStatus: EPEC_SDV.Status;      // status of temperature validation FB

S_EngineTemperature: SAFEDINT;               // valid temperature value

 

EngineTempAlarmDiagnostic: S_ValueDiagnostic;

EngineTempAlarmStatus:     EPEC_SDV.Status;

EngineTemperatureEC:       EPEC_DITF.EventCode;   

 

TempHighAlarmLimit:   SAFEDINT := DINT#150;  // alarm and warning limits, degrees of celsius

TempLowAlarmLimit:    SAFEDINT := DINT#-50;

 

 

 

Init at non-safe PRG:

 

 

EngineTemperatureEC.DeviceID := DeviceIDs.EngineTemperature;     // from app specific device enumeration

EngineTemperatureEC.ChannelID := ChannelIDs.Ch1;                  

EngineTemperatureEC.FunctionID := EPEC_DITF.FunctionIDs.NO_FUNC;

EngineTemperatureEC.EventID := EPEC_DITF.ErrorIDs.NO_ERROR;

 

(* init alarm FB *)

EngineTempAlarmDiagnostic.Init(

    S_i_HighErrorLimit := TempHighAlarmLimit,

    S_i_LowErrorLimit := TempLowAlarmLimit,

    S_i_EnableHighError := TRUE,

    S_i_EnableLowError := TRUE,

    S_i_DiagnosticDelay := 1000,   // 1 s delay

    S_i_SafeOutputValue := DINT#0,

    i_pEventCode := ADR(EngineTemperatureEC)

);

 

 

 

Code at non-safe PRG:

 

 

EngineTempAlarmDiagnostic(

    i_Enable := EngineTempValidStatus.OutputValid, // validation status

    S_i_Value := S_EngineTemperature,

    S_o_Output => ,

    o_Status => EngineAlarmStatus

);

 

 

 

See also