AB 西门子PLC的网络通讯实际讲座.ppt

网络介绍 Dilbert’s View on Future Technology Presentations Agenda Network Trends Producer/Consumer Model Ethernet - Overview ControlNet - Overview DeviceNet - Overview 分布式控制市场趋势 计算机网络的演变 分布式控制的演变 网络在自动化中追求的效率 Today’s networks operate faster than ever before Pure speed is no longer the issue - efficiency is The more efficient your network(s) handle data, the higher your throughput - the greater your productivity Example: Speed limits on highways have been increased, but do you arrive home any faster during “rush hour”? Producer/Consumer 模式 源/目标方式 源每次只能和一个目标通讯 每次通讯都必须有应答的过程 得到的速度是波特率 Producer/Consumer 方式 源发出信号，所有目标都是同时收到 不须有应答过程 得到的是数据率 NetLinx的三个核心元素 源/目标控制方式例子 NetLinx控制例子 Change-of-State - Sensor produces data only when object is present. Multicast - simultaneous data consumption. Cyclic - Analog I/O can send one value (pressure) every 50 ms, and another value (temperature) every 500 ms NetLinx的三个核心元素 源/目标采集方式例子 Master has to poll to collect all information Master passes data through control Logic to other devices NetLinx采集例子 Devices pass broadcast data status on a predetermined or event driven operation Any device can consume the data, if desired Reduce messaging, No programming NetLinx的三个核心元素 源/目标组态方式例子 If the network supports Configuration, often it is through the Master. Negatively impact Control performance, as the Master is burdened with tasks (Configuration) outside its main function (Control) If Configuration is not supported on the network - point-to-point, one at a time is your only option NetLinx组态例子 Programmable Device Support PC’s can communicate directly with the target devices This will not impact Control performance, as the Master is not burdened with tasks (Configuration) outside its main function (Control) If the user prefers, Configuration can be performed point-to-point with each device NetLinx 结构 RSLinx 通讯方式分类 (Examples) Source/Destination - “the classic model” - Profibus DP - Profibus PA - Interbus S - AS-i - Modbus - Modbu