Abstract: A real-time Ethernet named EtherMAC (Ethernet for Manufacture Automation Control) was developped for open computer numerical control system. A standard industrial personal computer (IPC) based master node and field programmable gate array (FPGA) based slave nodes were employed in EtherMAC, as neither dedicated network interface card (NIC) nor application specific integrated circuit (ASIC) chips were mandatory, the system was open in hardware architecture. The computation ability of IPC and hard real-time property of FPGA were combined together with Ethernet in this way. By adopting the first slave node to manage the communication and distributed clock, time critical performance could be achieved even the master node only with soft real-time performance. Experimental results showed that communication period less than 1 ms and synchronization precision within 100 ns could be achieved by EtherMAC, which were enough for motion control systems demanded critical real-time and synchronization.

Key words: synchronization, field programmable gate array, motion control, real-time Ethernet, communication period