I. Introduction? For a long time, the task of fail- safe communication technology can only be solved in the second layer using conventional means or distributed through a dedicated bus. This limits the living space of the distributed fieldbus PROFIBUS used in manufacturing and process industry automation. So far, PROFIBUS has been the only one that can meet the manufacturing industry (using RS485 and optical fiber transmission technology) and process industrial automation (using "MBP-IS", which is Manchester-encoded 1-bus power supply and intrinsically safe transmission because of its PROFIsafe fail-safe technology solution Technology, formerly known as IEC61158-2) Fieldbus required for fail-safe communication. 2. Main features of PROFIsafe The main features of PROFIsafe are summarized as follows: ◠Safety communication and standard communication coexist on the same cable; ◠PROFIsafe-fault safety is built on a single-channel communication system, safe communication does not use redundant cables to achieve the purpose; ◠Standard communication components, such as cables, dedicated chips (ASICS), DP-stack software, etc., without any changes; ◠Failure safety measures are enclosed in terminal modules (F-Master, F-Slave); ◠Using patented SIL monitor to obtain extremely high safety; ◠The highest fail-safety integrity level is SIL3 (IEC61508), and the corresponding German and European standards are AK6 (DIN V19250) and Kat.4 (EN954-1). SIL3:> 10-8 ... 10-7, that is, the failure rate per hour under continuous conditions; ◠PROFIsafe software solution can be flexibly applied to SIL 1, 2 or 3 equipment and safety control loop; ◠It can be used for both low-energy (Ex-i) process automation and rapid response manufacturing automation; ◠Environmental conditions are the same as standard PROFIBUS (anti-electromagnetic interference, etc.). ? 3. Communication principle: "Black Channel" and F- (Failsafe) layer structure PROFIsafe combines standard fieldbus technology and fail-safe technology into one system, ie fail-safe communication and standard communication coexist on the same cable. This not only saves a lot of money in wiring and variety diversity, but also can be rebuilt in the future. Users can naturally assign safety functions and standard functions to two PROFIBUS trunk lines based on organizational reasons (Figure 2). As can be seen from Figure 1, other safety bus systems can be connected via F-Gateway (F-Gateway). Process industry automation requires redundancy to increase equipment utilization. PROFIsafe adopts the method of single channel communication structure to make the realization of the above requirements very easy. Single channel fail-safe programmable controller can reach SIL3. In principle, this communication structure can also perform standard automation tasks, such as diagnosis, parameter setting server, etc. PROFIsafe is based on standard bus communication components—cables, chips, basic software packages (layer stacks), PROFIBUS-DP-master and PROFIBUS-DP-slave, etc., all of which are classified as "Black Channel". On the one hand, it means that all faults that may occur in "Black Channel" are detected by PROFIsafe; on the other hand, "Black Channel" does not have various functions to improve transmission security, so it does not involve the scope of safety technology. ISO / OSI simplified model 4 of PROFIsafe solution. As we all know, PROFIBUS uses only layers 1, 2 and 7 in the ISO / OSI-model. Fail-safe measures are placed in the safety layer above the layer 7-application layer (Safety-Layer). Since this layer is only responsible for the safe transmission of valid data, it requires the upper layer to be responsible for preparing and providing valid data, which is implemented by its technical firmware in a secure field device (eg, safety input). At least part of this type of firmware is usually designed in accordance with fail-safe technical requirements. Embedded PROFIsafe function in redundant hardware and software structure can also achieve the above purpose. As with standard operations, process signals and process data appear in corresponding valid messages. During safe operation, only these messages are supplemented (Figures 10 and 11). The transmitter signal originating from a modular slave station (a PROFIBUS station, which can contain several fail-safe modules with input / output channels) enters the two DP-master stations of the F-controller via the PROFIBUS slave connection point One of the connection points, from there, enters the F-controller via the local bus, the fail-safe CPU. An output signal generated after the connection enters the second DP-master connection point through the local bus again, and enters the second PROFIBUS trunk line. The transmission speed is reduced in the DP-PA link, using PA-Physical Transmission Technology (MBP-IS)-up to 31.25kBaud, and the signal is sent to the fail-safe PA-slave station. This signal does not use a redundant channel anywhere in its communication path, that is, the transmission is single channel. The above only discusses the communication path of the fail-safe message in detail. As for who is responsible for sending and when to send it, the answer is simple. The standard mechanism of PROFIBUS is used here, namely the master-slave operation mode. A master station-usually a CPU, exchanges messages with all its configured slave stations cyclically, that is, there is a 1: 1 relationship between the master station and the slave stations. The advantage of this type of polling operation (Polling) is that it can immediately detect a device that fails once, which is one of the basic principles of fail-safe technology. .Shell is made of high quality fire retardant PC material, up to the European environmental requirements, burning non-toxic. USB UL,USB UL data transfer cable,USB UL cable,Mini USB UL Hoojet Electric Appliance Co.,Ltd , https://www.hoojetgfci.com
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