Design and Implementation of Functional Safety Fieldbus Communication Protocol

Based on the requirements of safety communication in the safety instrumented system (SIS), a fieldbus functional safety communication protocol is proposed in this paper. According to the reasons of communication failure, several safety measures are used implicitly or explicitly to detect the error in the transmission. They include connection authentication, time stamp, sequence number and cyclic redundancy check (CRC). The communication architecture of full redundancy is structured to improve the reliability of communication system. Finally, the calculation results of the residual error rate show that the proposed functional safety fieldbus communication protocol meets the requirements of the safety integrity level (SIL) 3.