Abstract
Purpose. The authors according to requirements of the standard valid for safety-related communication between interlocking systems (EN 50159) analyze the situation of message undetected which is transmitted across BSC channel. The main part is orientated to description of model with CRC code used for messages assurance across noise communication channel. Methodology. For mathematical description of encoding, decoding, error detection and error correction is used algebra of polynomials. Findings. The determination of the intensity of dangerous failure caused by the electromagnetic interference was calculated. Originality. To obtain information on the probability of undetected error in transmission code and safety code and on the intensity of dangerous failure from the motel it was created program with graphical interface. To calculate the probability of undetected error for any block code (n, k) was created a supporting program that displays the probabilityof undetected error for selected interval of error bit rate. Practical value.From the measured and calculated values obtained by the simulation one can see that with increasing error bit rate is increasing also intensity of dangerous failures. Transmission code did not detect all corrupted messages therefore it is necessary to use safety code independent on transmission code in safety-related applications. CRC is not able to detect errors if all bits are logical 0.
Highlights
If the safety-related electronic system transfers information between different entities the communication system is part of a safetyrelated system and must be demonstrated that the transfer between end terminals is safe and in compliance with standard EN 50159 [5]
Time of the simulation was set to 100000 s for every error bit rate of binary symmetric channel to simulate transfer of 100000 messages with length 104 bits (64 bits of information part, safety code 32 bits and transmission code 8 bits)
The authors are in this papers dealing with the issue of safety-related communication and types of failures that may occur during transmission of safety-related messages
Summary
If the safety-related electronic system transfers information between different entities the communication system is part of a safetyrelated system and must be demonstrated that the transfer between end terminals is safe and in compliance with standard EN 50159 [5]. It is necessary to calculate the maximum value of probability of undetected error of code word in the transmission system for every safety code. If the error is not detected by transmission code nor safety code while the data integrity was corrupted by EMI during the transmission of the message the intensity of dangerous failure caused by EMI λEMI is calculated according to equation 6 [6]: λEMI = pSC . If we want to simulate transmission where the messages are affected only by functional block of binary symmetric channel (which generates random errors) S1 must be in position 1, on the position of S2 does not matter and S3 must be in position 1. If we want to simulate transmission where all bits are set to logical 1 the position of switches is as follows: S1 – does not matter, S2 – position 2, S3 – position 2
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