CalculateParameterIndexCRC (FUN)

Epec Programming and Libraries Manual

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Supported platforms: CODESYS 3.5, CODESYS 3.5 SAFETY

CalculateParameterIndexCRC (FUN)

Description

This function calculates checksum of a CANopen parameter index. The function uses function Calculate16bitCRC internally with parameters i_Seed = 0 and i_Polynomial = 1021h.

This function is intended to be used in device that configures safety unit. E.g. a display unit.

This function is endianness-aware.

Separate big-endian format conversions shall NOT be used.

Supported CANopen parameter index types

Code	Name	Supported
5	Deftype	No. Not used as application parameter.
6	Defstruct	No. Not used as application parameter.
7	Variable	Yes, if the variable type is supported.
8	Array	Yes, if the variable type is supported. Sub-index 0, i.e. the number of parameters is not counted to checksum.
9	Record	No. Record (=STRUCT) members has to be taken in count individually due data alignment and endianness issues.

See ParameterDataType table.

Limitations

STRUCT type parameter members need to be handled individually due data alignment and endianness issues.

BOOL, STRING and REAL are not supported as safe parameters.

Inputs

Input variable name	Data type	Range	Description
i_pData	POINTER TO BYTE	≠ 0	Pointer to parameters
i_DataType	ENUM	ParameterDataType	Parameter index data type.
i_NumberOfIndices	USINT	-	Number of parameters in index.

Outputs

Output variable name	Data type	Range	Description
o_OutputValid	BOOL	TRUE/FALSE	Calculated value is valid.
o_ParameterError	BOOL	TRUE/FALSE	Error in input parameters.

Return value

Data type	Description
WORD	Calculated checksum.

Error diagnostic

Conditions

Return value

o_OutputValid

o_ParameterError

i_pData = 0 OR

i_NumberOfIndices = 0

FALSE

TRUE

i_pData ok AND

i_DataType ok

Calculated result

TRUE

FALSE

Example code

Definitions:

SafetyParameterIndexCRCs: ARRAY[0..1] OF WORD := [2(WORD#0)];

Index2200: ARRAY[0..24] OF INT := [25(INT#0)];

Index2201: ARRAY[0..37] OF UDINT := [38(UDINT#0)];

(* Calculator output statuses *)

sparvalid: BOOL;

sparerror: BOOL;

Init:

No init.

Code:

SafetyParameterIndexCRCs[0] := EPEC_SDV.CalculateParameterIndexCRC(

i_pData := ADR(Index2200),

i_NumberOfIndices := USINT#25,

i_DataType := EPEC_SDV.ParameterDataType.Deftype_INTEGER16,

o_ParameterError => sparerror,

o_OutputValid => sparvalid

);

IF sparvalid THEN

SafetyParameterIndexCRCs[1] := EPEC_SDV.CalculateParameterIndexCRC(

i_pData := ADR(Index2201),

i_NumberOfIndices := USINT#38,

i_DataType := EPEC_SDV.ParameterDataType.Deftype_UNSIGNED32,

o_ParameterError => sparerror,

o_OutputValid => sparvalid

);

END_IF