EtherCAT has been taking the Semiconductor world by storm lately. The list of OEM (Original Equipment Manufacturer) investing in the technology is growing every week. Does that mean the DeviceNet protocol is dead in the Semiconductor world?
EtherCAT is a somewhat recent addition to the family of industrial protocol in the Fieldbus family. It was developed (and patented) by Beckhoff in Germany in 2003. It uses standard CAT5 type cabling and is compatible with existing routers and switches, but requires a specialized ASIC on the slave side of the network to achieve its high speed. This is great news for tool manufacturers since it greatly reduces the cost on the Master side: All you need is a PLC or PC with a standard (typically TI chip-set based) network card and standard CAT5 cables. In comparison, DeviceNet requires a special interface card costing over $1000, specialized cables, connectors, etc. Cost on the slave side are in the order of $10 for the special ASIC (also available in other form such as IP core for FPGA, and now being integrated into microcontroller such as the XMC4800 from Infineon), vs ~$5 for the slave DeviceNet solution.
As far as bandwidth, since EtherCAT utilizes the low level Ethernet protocol, it runs at the standard 100 Mbps, and is compatible with the newer 1Gbps speed. DeviceNet maxes out at 0.5Mbps. Typical cycle time on a DeviceNet Semi tool network is in the 10s of milliseconds. Typical cycle time on an EtherCAT network is 1 ms or below, down to 10s of microseconds, and with the addition of various clock modes, deterministic response in the sub microseconds are possible.
DeviceNet by design limits the number of nodes to 63 on one branch. EtherCAT allows 65 thousand node on each branch, and whereas DeviceNet cycle time increases proportionally with the number of nodes, the change in EtherCAT cycle time is negligible.
According to this article by HMS, industrial Ethernet is growing 20% a year while Fieldbus is growing at 7% a year. So while the EtherCAT protocol is fast replacing DeviceNet in the semiconductor worlds, the large install base of tools installed in the last 10 or 15 years means that shipment of DeviceNet nodes in the semiconductor markets will probably be in the hundreds of thousands for the next few years, while EtherCAT shipment for semiconductors is in the thousands, but all the new tools are being designed with EtherCAT protocol, and current generation tools are being upgraded as fast as possible to ship with EtherCAT. So slowly but surely, EtherCAT will dominate.
EtherCAT is a registered trademark of Beckhoff Automation and is managed by the EtherCAT Technical Group (ETG). DeviceNet was originally developed by Allen Bradley, and is now managed by the ODVA association. ODVA is also managing their version of industrial protocol: EtherNet/IP.
QFPS, llc offers expertise in the field of EtherCAT communications with specialization in the Semiconductor industry.
