A new real-time Ethernet for numeric control

This paper reviews real-time (RT) Ethernet and discusses special requirements for numerical control (NC). Then such a real-time Ethernet - EtherMAC (Ethernet for Manufacture Automation Control) is presented. EtherMAC uses master-slave communication structure. The master device supports standard Network Interface Card (NIC), and the slave device has a modified one - removing CSMA/CD (Carrier Sense Multiple Access / Collision Detection), changing logical link control (LLC) etc. EtherMAC's mechanism such as time-deterministic communication and synchronization is shown which is mainly controlled by the first node's sync frame. Besides, this paper analyzes its real-time performance and some drawbacks. At last, after an experiment which indicates that the synchronized latch signal's jitter error is random with boundary, some improvements are given based on the formula of the maximum jitter.