1、s machine combine, for resolve the very complicated problem to look for the best pathPLC language is not we imagine of edit collected materials the language or language of Cs to carry on weaving the distance, but the trapezoid diagram that the adoption is original after the electric appliances to co
2、ntrol, make the electrical engineering teacher while weaving to write the procedure very easy comprehended the PLC language, and a lot of non- electricity professional also very quickly know and go deep into to the PLC.Is PLC one of the advantage above and only, this is also one part that the people
3、 comprehend more and easily, in a lot of equipments, the people have already no longer hoped to see too many control buttons, they damage not only and easily and produce the artificial error easiest, small is not a main error perhaps you can still accept; But lead even is a fatal error greatly is wh
4、at we cant is tolerant of. New technique always for bringing more safe and convenient operation for us, make we a lot of problems for face on sweep but light, do you understand the HMI? Says the HMI here you basically not clear what it is, also have no interest understanding, change one inside text
5、explains it into the touch to hold or man-machine interface you knew, and it combines with the PLC to our larger space.When we are work a work piece, giving the PLC a signal, counting PLC inner part the machine add 1 to compute us for a day of workload, a count the machine and can solve problem in b
6、rief, certainly they also can keep the data under the condition of dropping the electricity, urging the data not to throw to lose, this is also what we hope earnestly.The PLC still has the function that the high class counts the machine, being us while accept some dates of high speed, the high speed
7、 that here say is the data of the in all aspects tiny second class, for example the bar code scanner is scanning the data continuously, calculating high-speed signal of the data processor DSP etc., we will adopt the high class to count the machine to help we carry on count. It at the PLC carries out
8、 the procedure once discover that the high class counts the machine to should of interruption, will let go of the work on the hand immediately. The trapezoid diagram procedure that passes by to weave the distance again explains the high class for us to carry out procedure to count machine would auto
9、matic performance to should of work, thus rise the Class that the high class counts the machine to high one Class.You heard too many this phrases perhaps: crash, the meaning that is mostly is a workload of CPU to lead greatly, the internal resources shortage etc. the circumstance cant result in proc
10、edure circulate. The PLC also has the similar circumstance, there is a watchdog WDT in the inner part of PLC, we can establish time that a procedure of WDT circulate, being to appear the procedure to jump to turn the mistake in the procedure movement process or the procedure is busy, movement time o
11、f the procedure exceeds WDT constitution time, the CPU turn but the WDT reset the appearance. The procedure restarts the movement, but will not carry on the breakage to the interruption.The PLC development has already entered for network ages of correspondence from the mode of the one, and together
12、other works control the net plank and 1/ O card planks to carry on the share easily. A state software can pass all se hardwires link, more animation picture of keep the view to carries on the control, and cans pass the Internet to carry on the control in the foreign land, the blast-off that is like
13、the absolute being boat No.5 is to adopt this kind of way to make airship go up the sky.The development of the higher layer needs our continuous effort to obtain. The PLC emergence has already affected a few persons fully, we also obtained more knowledge and precepts from the top one experience of t
14、he generation, coming to the continuous development PLC technique, push it toward higher wave tide.Knowing the available PLC network options and their best applications will ensure an efficient and flexible control system design.The programmable logic controllers （PLCs） ability to support a range of
15、 communication methods makes it an ideal control and data acquisition device for a wide variety of industrial automation and facility control applications. However, there is some confusion because so many possibilities exist. To help eliminate this confusion, lets list what communications are availa
16、ble and when they would be best applied.To understand the PLCs communications versatility, lets first define the terms used in describing the various systems.ASCII: This stands for American Standard Code for Information Interchange. As shown in Fig. 1, when the letter A is transmitted, for instance,
17、 its automatically coded as 65” by the sending equipment. The receiving equipment translates the ”65 back to the letter A.” Thus, different devices can communicate with each other as long as both use ASCII code.ASCII module: This intelligent PLC module is used for connecting PLCs to other devices al
18、so capable of communicating using ASCII code as a vehicle.Bus topology: This is a linear local area network （LAN） arrangement, as shown in Fig. 2A, in which individual nodes are tapped into a main communications cable at a single point and broadcast messages. These messages travel in both directions
19、 on the bus from the point of connection until they are dissipated by terminators at each end of the bus.CPU:central processing unit, which actually is that part of a computer, PLC, or other intelligent device where arithmetic and logical operations are performed and instructions are decoded and exe
20、cuted.Daisy chain: This is a description of the connection of individual devices in a PLC network, where, as shown in Fig. 3, each device is connected to the next and communications signals pass from one unit to the next in a sequential fashion.Distributed control: This is an automation concept in w
21、hich portions of an automated system are controlled by separate controllers, which are located in close proximity to their area of direct control （control is decentralized and spread out over the system）.Host computer: This is a computer thats used to transfer data to, or receive data from, a PLC in
22、 a PLC/computer network.Intelligent device: This term describes any device equipped with its own CPU.I/O:inputs and outputs, which are modules that handle data to the PLC （inputs） or signals from the PLC （outputs） to an external device.Kbps:thousand bits per second, which is a rate of measure for el
23、ectronic data transfer.Mbps:million bits per second.Node: This term is applied to any one of the positions or stations in a network. Each node incorporates a device that can communicate with all other devices on the network.Protocol: The definition of how data is arranged and coded for transmission
24、on a network.Ring topology. This is a LAN arrangement, as shown in Fig. 2C, in which each node is connected to two other nodes, resulting in a continuous, closed, circular path or loop for messages to circulate, usually in one direction. Some ring topologies have a special loop back feature that all
25、ows them to continue functioning even if the main cable is severed.RS232. This is an IEEE standard for serial communications that describes specific wiring connections, voltage levels, and other operating parameters for electronic data communications. There also are several other RS standards define
26、d.Serial: This is an electronic data transfer scheme in which information is transmitted one bit at a time.Serial port: This the communications access point on a device that is set up for serial communications.Star topology. This is a LAN arrangement in which, as shown in Fig. 2B, nodes are connecte
27、d to one another through a central hub, which can be active or passive. An active hub performs network duties such as message routing and maintenance. A passive central hub simply passes the message along to all the nodes connected to it.Topology: This relates to a specific arrangement of nodes in a
28、 LAN in relation to one another.Transparent: This term describes automatic events or processes built into a system that require no special programming or prompting from an operator.Now that were familiar with these terms, lets see how they are used in describing the available PLC network options.PLC network optionsPLC networks provide you with a variety of networking options to meet specific control and communications requirements. Typical options include remote I/O, peer-to-peer, and host computer communications, as well as LANs. These networks can provide reliable and cost-effect
