CalculateAccessCode (FUN)

Epec Programming and Libraries Manual

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Supported platforms: CODESYS 3.5, CODESYS 3.5 SAFETY

CalculateAccessCode (FUN)

Description

This function calculates response code from challenge code, Epec specific encryption keys, and project specific encrypting key value.

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

This function is endianness-aware.

Separate endian format conversions shall NOT be used.

Operation

The function calculates checksum of i_ProjectKey (STRING) with seed value 245Fh and polynomial 63D9h (prime numbers). The sum is used as seed for checksum calculation of i_ChallengeCode (WORD). The same polynomial is used in both phases.

Inputs

Input variable name	Data type	Range	Description
i_ChallengeCode	WORD	-	Challenge code to be compared
i_ProjectKey	STRING(80)	-	Data for code encryption

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 response code.

Error diagnostic

Conditions	Return value	o_OutputValid	o_ParameterError
i_ProjectKey length = 0	0	FALSE	TRUE
i_ProjectKey length > 0	Calculated result	TRUE	FALSE

Example code

Definitions:

ChallengeCode : WORD := WORD#0;

ResponseCode : WORD := WORD#0;

AccessCodeCalculationParError:BOOL;

AccessCodeCalculationValid:BOOL;

Init:

No init.

Code:

ResponseCode := EPEC_SDV.CalculateAccessCode(

i_ChallengeCode := ChallengeCode,

i_ProjectKey := 'MyProjectKey',

o_ParameterError => AccessCodeCalculationParError,

o_OutputValid => AccessCodeCalculationValid

);