Method of cable redundacy and distributed clock synchronization based on ethercat and master device thereof

A master device for EtherCAT, comprising:

• a processor;
• an Ethernet media access control module coupled to the processor;
• a junction unit comprising:
• a first connection port connected to the Ethernet media access control module;
• a second connection port for connecting a first slave device among a plurality of N slave devices that are connected in series;
• and
• a third connection port connected to an N-th slave device among the N slave devices;
• wherein the processor is configured to perform the following steps:
• step (1):
• sending a query datagram to instruct the junction unit and the N slave devices to report a plurality of port states to establish a network topology information based on the plurality of port states;
• step (2):
• based on the network topology information, determining whether there is a redundant connection, if yes, going to step (3), otherwise going to step (4);
• step (3):
• sending a first command datagram to disable a connection between the junction unit and the N-th slave device;
• step (4):
• performing a distributed clock synchronization procedure to calculate a plurality of system time delays in a redundant mode;
• step (5):
• based on the network topology information, determining whether there is a redundant connection, if yes, going to step (6), otherwise going to step (7);
• step (6):
• sending a second command datagram to enable the connection between the junction unit and the N-th slave device, wherein N is a natural number greater than 1;
• step (7):
• sending a periodic datagram to the junction unit and the N slave devices to synchronize a plurality of local system times of the junction unit and the N slave devices;
• step (8):
• when the network topology information indicates normal, going back to step (7);
• step (9):
• when the network topology information indicates a disconnection situation, going back to step (4) to calculate a plurality of system time delays with respect to the disconnection situation;
• and
• step (10):
• when the network topology information indicates that the disconnection situation is fixed, adopting the plurality of system time delays in the redundant mode, and going back to step (7).