The communication of PLC

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What the Part 5 of IEC61131 describes is the communication problem of PLC, the exchange that joins together how condition and control information come true between much stage PLC through communication network namely, how to start executive order. Executive command includes to start resource and download configuration to wait afresh. The communication service of IEC61131-5 includes two fields: Server equipment and client equipment. IEC61131-5 with international Organization for Standardization (ISO) the 7 agreements model of the network is a foundation, the communication model of IEC61131-5 was built on layer of the 7th application, so, go up from theory for, IEC61131-5 allows the network that any kinds carry between each PLC to have news report. A lot of ideas that define the communication equipment in IEC61131-5 come from IEC61131-3, if access method and communication functional piece. Communication function piece with relevant data type the concept in using IEC61131-3 and language will define. One. The communication model of communication model IEC61131-5 is shown like the graph. A PLC can be equivalent to a server, offer information and the request to the client to make response for the client, also can be equivalent to a client, ask information and requirement service to the server. The equipment of other, such as supervisory system (Supervisory System) with other blame IEC61131-3 photograph allows equipment to also can make server or client. Graph agreement of communication of one communication model (like aether net) the PLC server that allows to be not demarcate amount and client coexistence are in same a network is medium. Below a lot of circumstances, a PLC already a few OKer the server of PLC, can regard other as the client of a few PLC again. IEC61131-5 standard was defined merely in the communication equipment in PLC, be like the communication equipment of PLC A and B, external without definition other communication equipment of the client. IEC61131-5 regulation, each PLC can supply communication equipment at will in order to support the special application function below: Equipment examines data gains control the program is carried out and deferent user uses program of I/o control application the synchronous warning of the program reports join manages 2. If PLC function model pursues the 2 functional models that are PLC.

The executable program that use IEC61131-3 language defines needs the support of a lot of subsystem, long-range PLCs, equipment and supervisory system need communication service to monitor entirely their healthy circumstance and condition, in graph of certain circumstances 　 model condition leaves the function of 2 PLC, still need communication service to control each function subsystem. If supervisory system may need to access diagnostic program to be used at analysing program mistake, long-range perhaps PLC may need the healthy circumstance of surveillant PLC hardware to wait. 3. The state information IEC61131-5 of PLC stipulates PLC main subsystem expresses as follows: To each subsystem, the adoption that its state information uses form of a standard denotive data structure comes the data type in IEC61131-3 description. Each PLC subsystem have similar state item of information. Each subsystem has to call " Health(health condition) " initialization, it has 3 state: GOOD, WARNING, DAD. The state information of each subsystem still includes specific product condition information, such as diagnoses condition of mistake, operation to wait. Each subsystem can access a road to access state information easily via direct address through what define beforehand. IEC61131-5 defined to withhold direct address complexly to be used at accessing the condition of each subsystem inside PLC. If %S0 is advocate the direct address of PLC condition, %S3 is the direct address of condition of the 3rd subsystem. 4. Communication function piece IEC61131-5 standard allows information and control signal are exchanged between PLC. The communication equipment that next watches listed the standard is offerred and communication function piece. Join management (Connection Management) communication function piece read through communication channel write long-range PLC. Of communication channel building is through calling CONNECT the example of functional piece supplies the complete network address of long-range PLC what to CONNECT functional piece comes true. CONNECT function piece the label that returns channel of communication of a this locality, so, functional piece can use the full news report of need and specific long-range PLC communication this open communication channel. Equipment affirms (Device Verification) STATUS with UNSTATUS functional piece reads the facility that takes long-range PLC position. Data is obtained (Data Acquisition) what data obtains a care is read from long-range PLC take variable cost, read the method that takes variable cost to have two kinds: 1. Poll (Polled) : READ function piece can periodic ground or the cost that takes the variable that be chosen is read below specific trigger condition. 2. Process designing (Programmed) : Long-range PLC can decide why to be being planted data information is provided below the condition. The USEND inside long-range PLC functional piece can convey the without the request data that by URCV functional piece receives. Control (Control) those who two kinds of methods use at realizing local control software and long-range control software is alternant: 1. Parameter law (Parametric) : This kinds of method allows this locality PLC to adjust the behavior of long-range PLC through keeping a cost to crux variable. WRITE function piece allow to keep the cost long-range PLC inside elect " access method (Access Path) " in variable. 2. Each other locks up a law (Interlocked) : This kinds of method provided a kind of means that controls clerical processing, namely the signal that this locality PLC requests long-range PLC to carry out an operation to return an operation to finish then. Processing of this kind of general affairs is to pass PLC of use this locality (client) the function of the SEND inside piece with the RCV inside long-range PLC functional piece is finished. Newspaper alarm is accused (Alarm Report) call the police when what some books when the condition arises, PLC can issue signal to elect long-range PLC. Long-range PLC can send to affirm signal returns this locality PLC then, inform newspaper alarm to accuse had received. ALARM with NOTIFY functional piece can arise to affirm and be not affirmed newspaper warning to accuse. Variable limits manages (Variable Scope Management) variable limits management marked various IEC61131-3 languages or other are specific the name limits of implementation. 5. MMS map IEC61131-5 considered news report functional piece map arrives the production message of ISO/IEC 9605-5 is normative (MMS -Manufacturing Message Specification) the medium case that gives a service. The MMS spy application on MAP(Manufacturing Automation Protocol) layer.

MAP is the system of newsletter of a kind of industry that rolled out 1980 by global company of the United States at first.

MMS standard defined a series of services, these services allow industrial equipment, unit controller and supervisory system to exchange information through network of a communication. Each service is specific handle for a general affairs. A series of data that define beforehand be passed to give a long-range device, ask then a series of one in answering when define beforehand is made answer. Request information and answer information to have enough flexible will consider additional the implementation of specific data. The definition was included in the MMS map in the standard in the watch one in entire facility. Each functional piece uses the subclass that a MMS that already defined serves. Like STATUS functional piece will use MMS " condition " service. The implementation of each functional piece serves the MMS that calls a series of definitions. Between the equipment that this will permit to be allowed with IEC photograph can the network that have the aid of is based on MMS at either undertakes each other is operated. Use MMS to still can make those who be based on MMS network is not to use the equipment that IEC61131-3 standard realizes and the PLC that are based on IEC61131-3 standard to have news report. The numerical control machine tool that goes up in MMS network like (NC) can to be based on the STATUS inside the PLC of IEC61131-3 standard functional piece is made answer. IEC61131-5 defined the map between IEC61131-3 and MMS and corresponding data kind. IEC61131-5 still defined the compatibility regulation of data type, the map that still defined IEC61131-3 name limits to be handled to sundry MMS region and MMS general affairs. 6. Of the communication model that sums up IEC61131-5 build reach its communication functional piece arrives the production message of ISO/IEC 9605-5 is normative (MMS-Manufacturing Message Specification) of the medium map that gives a service build, not only from theoretic implementation the capacity that news report has through the network of any types between each PLC, and big still earth expanded PLC system and its automation control system are like numerical control machine tool (NC) , the robot have communication, compositive capacity. The future that IEC61131-5 standard got used to automation system well expands the requirement that raises to opening a gender, this makes IEC61131 OK suit well at next century. CNC Milling