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On the market there are many communication protocols. The most popular and widely used are certainly recognized standards such as Profibus DP, Profinet-IO, Modbus RTU, Modbus / TCP or EtherNet / IP. Choosing one of them depends mainly on the PLC control system provider, the technical parameters of the protocol and its price. Communication protocols are a set of strict rules and steps, automatically performed by a communications device to establish a connection and exchange data. Among the many communication standards can distinguish two groups of solutions, one of which is based on the Ethernet, while the other networks are field (fieldbus). By applying appropriate solutions to network communication is possible in the area of production lines, machinery and systems used in the enterprise. Selecting the communication standard should always be dependent on the network infrastructure requirements of the plant. At the forefront of protocols In a survey conducted by Control Engineering Poland that is most popular Profibus DP (Figure1). He says as much as81% of the surveyed users and 72% of suppliers. Profibus DP (Decentralized Periphery) is a simple, fast and deterministic protocol, which is regarded by millions of users as a leader in the field of distributed network, which since its inception, is undergoing continuous development. Due to the 20 years the presence of Profibus in the market is a well recognized and well refined, so you do not create major operational problems. For its advantages undoubtedly include: functionality and openness, easy to integrate devices from different manufacturers in a single system, resistance to interference, and - what is very important - a lot of support among manufacturers. It is no wonder that the Profibus DP is the most popular industrial network used for communication between the control system and peripherals. Currently, Profibus DP is available in three versions: DP-V0, DP-V1 and DP-V2. The first two versions of cyclic and acyclic allow EXCLUSIVELY Mian data between master and slave stations, and DP-V2 provides communication slave-to-slave isochronous (sync station is independent of the network load). Usually the transmission is implemented in RS-485 technology. According to a survey among the most popular protocols was also Modbus - developed over30 years ago by Modicon (now the company is owned by Schneider Electric). This protocol is relatively fast become a standard designed for industrial automation networks, while the company Modicon released it as a free, open communication protocol. Currently Modbus is a standard adopted by most manufacturers of industrial controllers for asynchronous communication between devices equipped with an interface compatible with RS-232 interface, such as RS-422, RS-485 modem. Time passed and Modbus interfaces are still present in today's network modules, in addition to newer standards, such as Ethernet or even Wi-Fi. The popularity and prevalence of Modbus decided such features as ease of use (both in the implementation and operation), disclosure protocol specification, secure messaging sent against error, effective safeguards against suspension system, confirming execution of remote commands and signaling errors or fixed frame format and a set of standard functions for data exchange. The Modbus protocol most often works with RS-485, which is now the base for many communication protocols used for remote programming, monitoring, control and data acquisition. RS-485 bus work in conditions of strong interference (for example,. Industry) and provides a large transmission ranges. Examples of Modbus applications include: remote data acquisition, industrial process control, supervision and protection systems, energy management, laboratory automation and so on. Importantly, through standard Modbus are capable of handling virtually all the most popular transmission media used in industrial applications: twisted pair - TP communication wireless, Ethernet, fiber, dial-up modems, mobile phones and many NON-INFRINGEMENT. Modbus RTU comes in at second place among the most well-known protocols specified by the surveyed users, and behind him came Modbus / TCP, often called Modbus over Ethernet. Due to the high popularity of devices with serial interface need for integration of devices communicating Modbus RTU with new devices having Ethernet interface, thereby communicating Modbus / TCP. Modbus RTU and Modbus / TCP can be converted using the appropriate tools, such as the goal of marking Mgate 3000, offered by Moxa. In the world of Ethernet One of the most popular standards in the wider industrial automation is certainly Ethernet, which especially in recent years has gained in popularity. For its use in the industry suggest factors such as: ensuring rapid and reliable communications at the device (eg. Between HMI, controllers, I / O modules, sensors and enforcement mechanisms) and the level connectivity information between computers at the plant, broad band data transmission, favorable price performance ratio Ethernet. In addition, one of the biggest advantages of Ethernet is its openness and flexibility, which draws attention to Krzysztof Getko, Product Manager of Schneider Electric Poland. - Architecture created based on Ethernet provide easy integration of multiple types of devices from different manufacturers through systems of managed switches or gateways. This feature is particularly important for integrators of automation systems. These systems are also easily extended to new device, which is very important for end customers who are planning for the future expansion of their plants. In addition, each network architecture based on Ethernet, we can design in several ways. Starting from the simple and low-cost serial bus, the more advanced the star or branched structures, to ring structures (Ring) and most reliable redundant rings (Redundant Ring). This allows you to optimize the costs and to achieve the required level of functionality and reliability - explains Krzysztof Getko. The undisputed leader in open industrial Ethernet networks is now EtherNet / IP (Industrial Protocol), defined by Rockwell Automation and supported by associating a few hundred members of ODVA. With EtherNet / IP is possible to use of CIP (Common Industrial Protocol) by classical Ethernet. This ensures compatibility with previously used equipment, Ethernet, and access to any data on the level of equipment, even from the Internet - with Ethernet and protocols TCP / IP and UDP / IP. In addition, the EtherNet / IP is ideal for a large amount of data, due to a high rate (10/100 Mb / s). Data transmission can take place in two ways - periodically or acyclic. It is worth noting that the EtherNet / IP is promoted by companies such as Parker Hannifin, Phoenix Contact, Rockwell Automation, Sick, Omron, Bosch. Another popular industrial Ethernet network is Profinet, an international organization created by Profibus International. Thanks to the modular structure of Profinet is widely used in all branches of industry, in particular in the automotive industry, the construction machinery, food industry and logistics. Solutions based on Profinet can be implemented with the production and process automation, security applications, as well as any technology attacks, including isochronous positioning systems. Profinet-IO standard has been recognized by the persons involved in the survey as the most dynamically developing communication protocol (Figure4). It is a combination of easy to use Profibus DP with standard Ethernet physical layer, allowing compatibility with both conventional Ethernet devices, and formerly used as industrial automation devices. Profinet-IO because of the many advantages is often used by many systems integrators and manufacturers of equipment and machinery. Its advantages include: increased speed and facilitating the management of the growing amount of data, the ability to integrate the standard Ethernet data transmission. In addition, the standard features parameterization, diagnostics and alarms available on the Profinet-IO are more powerful than conventional bus systems. With Profinet protocol used by, among others, companies such as Phoenix Contact, Siemens, Beckhoff, Danfoss, Bosch Rexroth. It is worth mentioning that among the protocols most widely under the heading "Other" are set m.in .: Foundation Fieldbus, DNP3, Uni-Telway, ControlNet and IEC 61850 (he was also among the "other" most dynamically developing protocols ). Ethernet future? Due to the growing interest in Ethernet protocols we asked our respondents whether, in their opinion, they replace other solutions in the future. It turns out that as much as76% of users and 61% of suppliers believe that this is the most realistic vision of the future (Figure2). Anticipate are the factors such as increasing opportunities and the increasingly lower prices Ethernet solutions, simple implementation, the ability to transfer larger amounts of data, increasing transmission speed, high bandwidth (so one cable can be used by multiple systems), greater flexibility in compared to protocols that are not based on Ethernet, reliability and confidence connection. The remaining group of respondents believe that, despite the many advantages and the popularity of the probability of dominance over other Ethernet protocols is very small. - This is primarily a very broad and diverse base of installed equipment in industrial, technical limitations of these protocols or even the specialization of certain communications standards for specific industries, for example. AS-i HART - explains Krzysztof Getko. Conversely, according to Peter Gocłowski, Product Manager of the company Elmark Automation, migration producers and consumers to networks based on Ethernet is only a matter of time. This is inevitable, but it may still take some time, because in many places systems based on serial busses (Modbus RTU, Profibus) will work for a long time without requiring modernization. - In addition, communication gateway / protocol converters provide a "contact" with such networks using protocols based on Ethernet. In some areas the transition to Industrial Ethernet is not necessary and does not bring large benefits. For example, the CAN network is very optimal for applications in which it is used - in communication peripherals, microcontrollers and sensors in vehicles. So there are fields where serial communication is the most favorable and sufficient. Integration of industrial networks with LAN and WAN carries a lot of benefits, but the other side of the coin is easier unauthorized access to such networks and the danger of hacker attacks. An example of such an attack on the network very well protected, and without access to the WAN was the Stuxnet virus. He was so advanced that it could spread to pendrive'ach and infect the Siemens software configuration PLC, which in clear reasons was very dangerous for the object. So combining industrial networks to the Internet or even local networks carries some risk - warns Peter Gocłowski. A problem related to security and unauthorized access also mentions Peter Mendera, a specialist from the company RAControls automatic exchanging weaknesses solutions based on Ethernet protocols. In his opinion these solutions, in addition to numerous advantages, they also have - in addition to the above. defects - even one big minus, which is the high price of network infrastructure (managed switches, VPN, fiber optic technology, etc..) unnecessarily used in places where he successfully suffice plain wire cable. According to Piotr Adamczyk, product manager of the company ASTOR, the only right direction for a network based on the Ethernet standard. Opportunities offered by this standard meets current customer expectations while providing quick and easy system expansion by new elements. - In my opinion, the trend of changes in the direction of Ethernet will continue. In subsequent years, should gain faster Ethernet area previously dominated by deterministic protocols, how fast I / O and systems to synchronize axis. The next step will be frequent use of wireless communications in industrial communication. Serial Protocols will still be used to connect older devices or budget - says Krzysztof Hajzyk, Regional Sales Manager from ProSoft Technology. From the observation of Martin Marcińczyk, commercial and technical consultant of the company InduProgress that, although guided by the market towards protocols based on Ethernet solutions, smaller companies - due to continued higher costs - opt for simpler and cheaper solutions at the same time. Supplier PLC and technical parameters As according to a survey, the main criteria taken into account when choosing a communication protocol are primarily supplier PLC and technical parameters (Figure3). The following positions were factors such as the requirements of end customers and price communication protocols, which, in the opinion of more than half (57%) of respondents is relevant to their life opportunities. In addition, among the answers given by the suppliers in the "other" included such factors as previous network infrastructure in a plant, a simple configuration in one place, the ability to connect devices from different suppliers into one coherent system of control, speed and amount of data, your data is secure and the reliability of communication. Plans buying and selling vision As many as 71% of users surveyed have plans in the coming months to increase spending on solutions based on Ethernet communication protocols. According to the responses of people interviewed mainly due to the fact that Ethernet has become the standard in the industry, the most versatile media network, which is characterized by ease of use and high flexibility, efficiency and relatively low cost of implementation. For completeness it is worth noting that19% of people think that the cost will remain unchanged, and10% say they will decrease. As far as the budget for the purchase of communications protocols that are not based on Ethernet, it turns out that the 43% of users in the coming months they will not change. The remainder of the respondents believe that will increase (33%) or decrease (24%). What's this have to say about respondents supplier? As according to a survey, everyone is convinced that in the coming months to increase the sales of solutions based on Ethernet communication protocols. In terms of the expected sale solutions niebazujących on Ethernet, is, according to suppliers (56%) in the coming months should not expect major changes. The remainder of the respondents is divided evenly into two groups, one of which believes that the next time will bring an increase in sales, while the second predicts a decline. The report was based on data obtained from a survey conducted in September 2013. Among the readers of Control Engineering Poland. In addition, when creating the report was based on information from the suppliers protocols.
Modbus RTU and Modbus published by Modicon
Profibus DP used by Siemens
Profibus, modbus rtu, canbus, ethernet
rs232, rs482
Profibus and modbus
Standard Ethernet Protocols
Most Commonly used protocols are Modbus, Profibus.
Mod-Bus ,Profi-Bus and Ethernet are mostly famous protocols used in Industrial automation.RS-232 and RS482 are also uses in some places for different no of hosts.
