DCS Industrial Protocols Extract


DCS Industrial Protocols Used within Industry Extract


Dominant protocols in the process automation sector are Fieldbus variants (PROFINET, FOUNDATION Fieldbus) and Common Industrial Protocol (CIP) derivatives. IEC 61158 and IEC 61784 contain profiles for each major Fieldbus variant.


DF1 is a serial communications protocol defined in ANSI X3.28, subparagraphs D1 and F1. The protocol, originally developed by Allen-Bradley (now owned by Rockwell Automation), is often used as the mechanism to deliver programmable controller communications commands (PCCCs) to Allen-Bradley PLCs.


FOUNDATION Fieldbus is suited for applications using basic and advanced regulatory control and for much of the discrete control associated with those functions. There are two implementations of FOUNDATION Fieldbus running at different speeds and over different physical media: H1, the most common implementation, generally connects field devices and runs at 31.25Kbps; HSE (high-speed Ethernet) connects hosts, I/O subsystems, gateways, and field devices, and runs at 100 Mbps. FOUNDATION Fieldbus is included as a Fieldbus in IEC 61804.


Profibus – Process Field Bus
Profibus was developed by BMBF, the German department of education and research. It has two variations. The more popular variation, Decentralized Peripherals (DP), is used for sensor/actuator operation via a centralized controller. The other variation, Process Automation (PA), monitors measuring equipment via a PCS. PA is designed for use in explosive and hazardous areas and uses a physical layer that conforms to IEC 61158-2. PA uses the same protocol as DP but runs at 31.25Kpbs. A coupler can be used to interface a DP network to a PA network, with the DP being used as a backbone. Profibus is included as a Fieldbus in IEC 61158 and IEC 61784.


The PROFINET concept features two perspectives—PROFINET CBA and PROFINET IO— both of which can communicate at the same time on the same bus system. They can be operated separately or combined so that a PROFINET IO subsystem can appear as a PROFINET CBA system from another perspective. PROFINET IO was developed for real-time (RT) and isochronous real-time (IRT) communication with the decentral periphery. RT has a 10 ms cycle time. IRT drives systems with cycle times of 1 ms or less. PROFINET CBA is suitable for component-based communication via TCP/IP and the real-time communication for real-time requirements in modular systems engineering. Both communication options can be used in parallel. PROFINET CBA has a reaction time in the range of 100 ms. PROFINET is included as a Fieldbus in IEC 61158 and IEC 61784.


CC-Link was originally developed by Mitsubishi and has seen large adoption as a fieldbus by Japanese vendors.There are more than 6 million CC-Link devices deployed, and more than 1000 different devices exist. With CC-Link Industrial Ethernet, CC-Link can be integrated with typical IT networks.
There are four CC-Link formats:
• CC-Link
• CC-Link LT (lightweight version for lower device communication)
• CC-Link Safety (high reliability, compliant w/IEC 61508 SIL3 and ISO13849-1 Cat 4)
• CC-Link IE (Industrial Ethernet).
Typical CC-Link communication media include twisted pair and fiber optic. The CC-Link Partner Association provides a list of domestic and international partners.


Common Industrial Protocol (CIP)
Common Industrial Protocol (CIP) provides a unified communications architecture throughout the manufacturing sector. It can be seen as a common application layer to EtherNet/IP, DeviceNet, CompoNet, and ControlNet. CIP encompasses a comprehensive suite of messages and services for the collection of manufacturing automation applications—control, safety, synchronization, motion, configuration, and information. The protocol is managed by Open DeviceNet Vendors Association (ODVA).


ControlNet is an implementation of CIP originally developed by Allen-Bradley. ControlNet has a built-in ability to support fully redundant link cables, and all communication is strictly scheduled and highly deterministic. The ControlNet physical layer is either RG-6 coaxial using BNC connectors or optical fiber. ControlNet uses Manchester encoding, and the bus speed is 5 Mbps. The link layer operates in cycles known as network update times (NUTs), with each NUT having two phases, the first of which is reserved for scheduled traffic transmission to guarantee a transmission opportunity, and the second of which is for unscheduled traffic transmission without any guarantee. The maximum frame size is 510 bytes.


DeviceNet is an implementation of CIP originally developed by Allen-Bradley. DeviceNet is layered on top of the Controller Area Network (CAN) physical layer and adapts ControlNet technology. It is low-cost and robust compared to traditional RS-485 based protocols. DeviceNet operates at baud rates of 125 Kbps, 250 Kbps, and 500 Kbps. Trunk length is inversely proportional to the speed of the bus—i.e., 500, 250, and 125 meters, respectively. The majority of installations use a master/slave configuration, but peer-to-peer is possible. Multiple masters can exist on a single logical network. DeviceNet is engineered to withstand noisy environments.


EtherNet/IP is an implementation of CIP originally developed by Rockwell Automation. The protocol’s application layer is CIP. EtherNet/IP is an application layer protocol built on the standard TCP/IP stack that considers all devices on the network as a series of “objects.” It makes use of existing Ethernet infrastructure (regardless of speed). An entire EtherNet/IP stack can be implemented in software on a microprocessor without the need for ASICs or field-programmable gate arrays (FPGAs). EtherNet/IP makes use of 44818/TCP for explicit messaging and 2222/UDP for implicit messaging.


EtherCAT – Ethernet for Control Automation Technology
EtherCAT is an Ethernet-level protocol with Ethertype 0x88A4, with IP routing possible by insertion of frames into UDP datagrams. Rather than processing one frame per node per cycle (update time), EtherCAT uses “processing on the fly.” Rather than an Ethernet frame being received, then interpreted and copied as process data at every node, EtherCAT slave devices read the data addressed to them while the datagram passes through the device. Similarly, input data are inserted while the datagram passes through. Many nodes can be addressed with one frame.
Gateways are available to integrate EtherCAT networks with CANopen, DeviceNet, PROFIBUS, and other protocols. The EtherCAT Technology Group is the international user and vendor organization; it consists of over 1100 companies from 47 countries as of August 2009. EtherCAT is included as a fieldbus in IEC 61158 and IEC 61784.
EtherCAT uses ports 34980/UDP and 34980/TCP to route between Ethernet LANs.


EGD – Ethernet Global Data
Ethernet Global Data (EGD) is a mechanism that enables one CPU to share a portion of its internal reference memory with one or more other CPUs at a regularly scheduled periodic rate. EGD is used by some GE Fanuc PLCs.


FINS is a protocol developed by Omron (a Japanese controls company) for use in many of its newer PLCs. It typically runs on IP-enabled systems using port 9600/UDP.


EGD – Ethernet Global Data
Ethernet Global Data (EGD) is a mechanism that enables one CPU to share a portion of its internal reference memory with one or more other CPUs at a regularly scheduled periodic rate. EGD is used by some GE Fanuc PLCs.


Host Link
Host Link is a protocol developed by Omron for its older PLC line; however, many new Omron PLCs can still communicate using HostLink. It is an ASCII-based, RS-232 protocol.


SERCOS Interface – Serial Real-Time Communication System
SERCOS has hard real-time requirements and is particularly useful in motion controls, e.g., metal cutting and forming, assembly machinery, packaging, robotics, printing, and materials handling. The protocol is governed by SERCOS International. The current version is SERCOS-
III. SERCOS is defined in IEC 61158 and IEC 61784.


SRTP – Service Request Transfer Protocol
SRTP is a protocol used to communicate commands and data to/from PLCs from PCs. It is used by GE Fanuc PLCs as an application layer.


Sinec H1
Sinec H1 is a transport layer developed by Siemens. Different application layers may run on top of it. Its large bandwidth makes it ideal for large data volume transmission





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