Method for detecting communication disturbances in a master-slave
system (20), wherein the master-slave
system (20) comprises a master unit (21) and at least one slave unit (22, 23, 24), wherein the at least one slave unit (22, 23, 24) is connected to the master unit (21) via a communication
system (25), wherein the communication system (25) has a safety
bus (26), and wherein the at least one slave unit (22, 23, 24) has a safety module (27), wherein the master unit (21) communicates with the at least one slave unit (22, 23, 24) via the safety
bus (26) in safety cycles, wherein during a safety cycle the master unit (21) transmits data to be processed by the safety module (27) of the at least one slave unit (22, 23, 24) to the at least one slave unit (22, 23, 24), and wherein the method (1,10) has the following steps: - Defining a
limit value for a time during which each slave unit (22,23,24) cannot receive any data to be processed by the safety module (27) of the slave unit (22,23,24) without an
error message being issued (2,11); and for each slave unit (22, 23, 24), check whether the slave unit (22, 23, 24) has received data to be processed by the security module (27) of the slave unit (22, 23, 24) from the master unit (21) during the safety cycle (3, 12), wherein, if the slave unit (22, 23, 24) has not received any data to be processed by the security module (27) of the slave unit (22, 23, 24) from the master unit (21) during the safety cycle, a period is determined which indicates how long the slave unit (22, 23, 24) has not received any data to be processed by the security module (27) of the slave unit (22, 23, 24) from the master unit (21) (4, 13), wherein the period is compared with the
limit value (5,14), and wherein, if the period is greater than the
limit value, it is determined that a communication fault has occurred (6, 15), wherein the procedure (10) further comprises the following step:
synchronizing the safety
bus (26) to a master communication (17); and wherein a last slave unit (22, 23, 24) in a communication ring has master functionality, and wherein the step (17) of
synchronizing the safety bus (26) to the master communication comprises the following step: specifying a
start time for a new safety cycle by the last slave unit (22, 23, 24) based on the master communication.