外文翻译理解s7200网络通讯的基本概念

Understanding the Basics of S7-200 Network CommunicationsSelecting the Communication Interface for Your NetworkThe S7-200 is designed to solve your communications and networking needs by supporting not only the simplest of networks but also supporting more complex networks. The S7-200 also provides tools that allow you to communicate with other devices, such as printers and weigh scales which use their owncommunications protocols.The S7-200 supports many different types of communication networks. The selection of a network isperformed within the Set PG/PC Interface property dialog. A selected network is referred to as an Interface. The different types of interfaces available to access these communication networks are:1. PPI Multi-Master cables2. CP communication cards3. Ethernet communication cardsTo select the communication interface for STEP 7-Micro/WIN, you perform the following steps. See Figure 7-1.1. Double-click the icon in the Communications Setup window.2. Select the interface parameter for12Figure 7-1 STEP 7-Micro/WINCommunications InterfacePPI Multi-Master CablesThe S7-200 supports communication through two different types of PPI Multi-Master cables. These cable types permit communication through either an RS-232 or a USB interface.As shown in Figure 7-2, selecting the PPI Multi-Master cable type is simple. You perform the following steps:1. Click the Properties button on the Set PG/PC Interface property page.2. Click the Local Connection tab on the Properties page.3. Select the USB or the desired COM port .132Figure 7-2 PPI Multi-Master Cable SelectionTipPlease note that only one USB cable can be used at a time.TipExamples in this manual use the RS-232/PPI Multi-Master cable. The RS-232/PPI Multi-Master cable replaces the previous PC/PPI cable. A USB/PPI Multi-Master cable is also available. Refer to Appendix E for order numbers.Using Master and Slave Devices on a PROFIBUS NetworkThe S7-200 supports a master-slave network and can function as either a master or a slave in a PROFIBUS network, while STEP 7-Micro/WIN is always a master.MastersA device that is a master on a network can initiate a request to another device on the network. A master can also respond to requests from other masters on the network. Typical master devices include STEP 7-Micro/WIN, human-machine interface devices such as a TD 200, and S7-300 or S7-400 PLCs. The S7-200 functions as a master when it is requesting information from another S7-200 (peer-to-peer communications).TipA TP070 will not work on a network with another master device.SlavesA device that is configured as a slave can only respond to requests from a master device; a slave never initiates a request. For most networks, the S7-200 functions as a slave. As a slave device, the S7-200 responds to requests from a network master device, such as an operator panel or STEP 7-Micro/WIN.Setting the Baud Rate and Network AddressThe speed that data is transmitted across the network is the baud rate, which is typically measured in units of kilobaud (kbaud) or megabaud (Mbaud). The baud rate measures how much data can be transmitted within a given amount of time. For example, a baud rate of 19.2 kbaud describes a transmission rate of 19,200 bits per second.Every device that communicates over a given network must be configured to transmit data at the same baud rate. Therefore, the fastest baud rate for the network is determined by the slowest device connected to the network.Table 7-1 lists the baud rates supported by the S7-200.Table 7-1 Baud Rates Supported by the S7-200NetworkBaud RateStandard Network9.6 kbaud to 187.5 kbaudUsing an EM 2779.6 kbaud to 12 MbaudFreeport Mode1200 baud to 115.2 kbaudThe network address is a unique number that you assign to each device on the network. The unique network address ensures that the data is transferred to or retrieved from the correct device. The S7-200 supports network addresses from 0 to 126. For an S7-200 with two ports, each port has a network address. Table 7-2 lists the default (factory) settings for the S7-200 devices.Table 7-2 Default Addresses for S7-200 DevicesS7-200 DeviceDefault AddressSTEP 7-Micro/WIN0HMI (TD 200, TP, or OP)1S7-200 CPU2Setting the Baud Rate and Network Address for STEP 7-Micro/WINYou must configure the baud rate and network address for STEP 7-Micro/WIN. The baud rate must be the same as the other devices on the network, and the network address must be unique. Typically, you do not change the network address (0) for STEP 7-Micro/WIN. If your network includes another programming package, you might need to change the network address for STEP 7-Micro/WIN.As shown in Figure 7-3, configuring the baud rate and network address for STEP 7-Micro/WIN is simple. After you click the Communications icon in the Navigation bar, you perform the following steps:1243Figure 7-3 Configuring STEP 7-Micro/WIN1. Double-click the icon in the Communications Setup window.2. Click the Properties button on the Set PG/PC Interface dialog box.3. Select the network address for STEP 7-Micro/WIN.4. Select the baud rate for STEP 7-Micro/WIN.Setting the Baud Rate and Network Address for the S7-200You must also configure the baud rate and network address for the S7-200. The system block of the S7-200 stores the baud rate and network address. After you select the parameters for the S7-200, you must download the system block to the S7-200.The default baud rate for each S7-200 port is 9.6 kbaud, and the default network address is 2.As shown in Figure 7-4, use STEP 7-Micro/WIN to set the baud rate and network address for the S7-200. After you select the System Block icon in the Navigation bar or select the View Component System Block menu command, you perform the following steps:1. Select the network address for the S7-200.2. Select the baud rate for the S7-200.3. Download the system block to the S7-200.12Figure 7-4 Configuring the S7-200 CPUTipSelection of all baud rate options is permitted. STEP 7-Micro/WIN validates this selection during the download of the System Block. Baud rate selections that would prevent STEP 7-Micro/WIN from communicating with the S7-200 are prevented from being downloaded.Setting the Remote AddressBefore you can download the updated settings to the S7-200, you must set both the communications (COM) port of STEP 7-Micro/WIN (local) and the address of the S7-200 (remote) to match the current setting of the remote S7-200. See Figure 7-5.After you download the updated settings, you may need to reconfigure the PG/PC Interface baud rate setting (if different from the setting used when downloading to the remote S7-200). Refer to Figure 7-3 to configure the baud rate.Figure 7-5 Configuring STEP 7-Micro/WINSearching for the S7-200 CPUs on a NetworkYou can search for and identify the S7-200 CPUs that are attached to your network. You can also search the network at a specific baud rate or at all baud rates when looking for S7-200s.Only PPI Multi-Master cables permit searching of all baud rates. This feature is not available if communicating through a CP card. The search starts at the baud rate that is currently selected.1. Open the Communications dialog box and double-click the Refresh icon to start the search.2. To search all baud rates, select the Search All Baud Rates check box. 2.Selecting the Communications Protocol for Your NetworkThe following information is an overview of the protocols supported by the S7-200 CPUs.1. Point-to-Point Interface (PPI)2. Multi-Point Interface (MPI)3. PROFIBUSFigure 7-6 Searching for CPUs on a NetworkBased on the Open System Interconnection (OSI) seven-layer model of communications architecture, these protocols are implemented on a token ring network which conforms to the PROFIBUS standard as defined in the European Standard EN 50170. These protocols are asynchronous, character-based protocols with one start bit, eight data bits, even parity, and one stop bit. Communications frames depend upon special start and stop characters, source and destination station addresses, frame length, and a checksum for data integrity. The protocols can run on a network simultaneously without interfering with each other, as long as the baud rate is the same for each protocol.Ethernet is also available for the S7-200 CPU with expansion modules CP243-1 and CP243-1 IT.PPI ProtocolPPI is a master-slave protocol: the master devices send requests to the slave devices, and the slave devices respond. See Figure 7-7. Slave devices do not initiate messages, but wait until a master sends them a request or polls them for a response.Masters communicate to slaves by means of a shared connection which is managed by the PPI protocol. PPI does not limit the number of masters that can communicate with any one slave; however, you cannot install more than 32 masters on the network.Figure 7-7 PPI NetworkS7-200 CPUs can act as master devices while they are in RUN mode, if you enable PPI master mode in the user program. (See the description of SMB30 in Appendix D.) After enabling PPI master mode, you can use the Network Read or the Network Write instructions to read from or write to other S7-200s.While the S7-200 is acting as a PPI master, it still responds as a slave to requests from other masters.PPI Advanced allows network devices to establish a logical connection between the devices. With PPI Advanced, there are a limited number of connections supplied by each device. See Table 7-3 for the number of connections supported by the S7-200.All S7-200 CPUs support both PPI and PPI Advanced protocols, while PPI Advanced is the only PPI protocol supported by the EM 277 module.Table 7-3 Number of Connections for the S7-200 CPU and EM 277 ModulesModuleBaud RateConnectionsS7-200 CPU Port 0 Port 19.6 kbaud, 19.2 kbaud, or 187.5 kbaud49.6 kbaud, 19.2 kbaud, or 187.5 kbaud4EM 277 Module9.6 kbaud to 12 Mbaud6 per moduleMPI ProtocolMPI allows both master-master and master-slave communications. See Figure 7-8. To communicate with an S7-200 CPU, STEP 7-Micro/WIN establishes a master-slave connection. MPI protocol does not communicate with an S7-200 CPU operating as a master.Network devices communicate by means of separate connections (managed by the MPI protocol) between any two devices. Communication between devices is limited to the number of connections supported by the S7-200 CPU or EM 277 modules. See Table 7-3 for the number of connections supported by the S7-200. For MPI protocol, the S7-300 and S7-400 PLCs use the XGET and XPUT instructions to read and write data to the S7-200 CPU. For information about these instructions, refer to your S7-300 or S7-400 programming manual.Figure 7-8 MPI NetworkPROFIBUS ProtocolThe PROFIBUS protocol is designed for high-speed communications with distributed I/O devices (remote I/O). There are many PROFIBUS devices available from a variety of manufacturers. These devices range from simple input or output modules to motor controllers and PLCs.PROFIBUS networks typically have one master and several slave I/O devices. See Figure 7-9. The master device is configured to know what types of I/O slaves are connected and at what addresses. The master initializes the network and verifies that the slave devices on the network match the configuration. The master continuously writes output data to the slaves and reads input data from them.Figure 7-9 PROFIBUS NetworkWhen a DP master configures a slave device successfully, it then owns that slave device. If there is a second master device on the network, it has very limited access to the slaves owned by the first master.TCP/IP ProtocolThe S7-200 can support TCP/IP Ethernet communication through the use of an Ethernet (CP 243-1) orInternet (CP 243-1 IT) expansion module. Table 7-4 shows the baud rate and number of connections supported by these modules.Table 7-4 Number of Connections for the Ethernet (CP 243-1) and the Internet (CP 243-1 IT) ModulesModuleBaud RateConnectionsEthernet (CP 243-1) Module10 to 100 Mbaud8 general purpose connectionsInternet (CP 243-1 IT) Module1 STEP 7-Micro/WIN connectionRefer to the CP 243-1 Communications Processor for Industrial Ethernet Manual or the CP 243-1 IT Communications Processor for Industrial Ethernet and Information Technology Manual for additional information.中文翻译理解S7-200网络通讯的基本概念为网络选择通讯接口S7-200可以满足您的通讯和网络需求，它不仅支持简单的网络，而且支持比较复杂的网络。S7-200提供了通讯手段，使您可以用它与那些使用自己的通讯协议的设备，例如：打印机和称重天平等进行通讯。S7-200可以支持各种类型的通讯网络。在SET PG/PC Interface属性对话框中进行网络选择。一个选定的网络将被作为一个接口来使用。能够访问这些通讯网络的各类接口包括：1.多主站PPI电缆2.CP通讯卡3.以太网通讯卡通过下列步骤，您可以为STEP 7-Micro/WIN选择通讯接口。参见图7-1。1. 在通讯设置窗口中双击图标。2. 为STEP 7-Micro/WIN选择接口参数。多主站PPI电缆S7-200可以通过两种不同类型的PPI多主站电缆进行通讯。这些电缆允许通过RS-232或USB接口进行通讯。如图7-2所示，选择PPI多主站电缆的方法很简单。只需执行以下步骤即可：1. 在Set PG/PC Interface属性页中，点击属性按钮。2. 在属性页中，点击本地连接标签。3. 选中USB或所需的COM端口。提示请注意，一次只能使用一个USB接口。提示本手册的实例使用的是RS-232/PPI多主站电缆。原先的PC/PPI电缆已RS-232/PPI多主站电缆替代。另外，USB/PPI电缆也适用于这些实例。关于这些电缆的订货号，可参见附录C。在PROFIBUS网络上使用主站和从站器件。S7-200支持主-从网络，并能在PROFIBUS网络中充当主站或从站，而STEP 7-Micro/WIN只能作为主站。主站网络上的主站器件可以向网络上的其它器件发出要求。主站也可以对网络上其它主站的要求作出响应。典型的主站器件包括：STEP 7-Micro/WIN、TD200等HMI产品和S7-300或S7-400 PLC。在向其它S7-200发出请求以获取信息（点对点通讯）时，S7-200是作为主站的。提示如果网络上有其它主站，TP070将无法工作。从站配置为从站的器件只能对其它主站的要求作出响应，自己不能发出要求。对于多数情况，S7-200被配置为从站。作为从站，S7-200响应主站的要求。作为从站时，S7-200将负责响应来自某网络主站器件（如操作员面板或STEP 7-Micro/WIN）的请求。设置波特率和站地址数据通过网络传输的速度是波特率。其单位通常为Kbaud或者Mbaud。波特率用于量度在给定时间内传输数据的多少。比如，19.2k的波特率即表示传输速率为每秒19200比特。在同一个网络中通讯的器件必须被配置成相同的波特率。因此，网络的最高波特率取决于连接在该网络上的波特率最低的设备。表7-1中列出了S7-200支持的波特率。表7-1 S7-200支持的波特率网络波特率标准网络9.6K到187.5K使用EM2779.6K到12M自由口模式1200到115.2K在网络中要为每个设备指定唯一的站地址。唯一的站地址可以确保数据发送到正确的设备或者来自正确的设备。S7-200支持的网络地址为从0到126。如果某S7-200带有两个端口，那么每个端口都会有一个网络地址。表7-2列出了S7-200设备的缺省（工厂）设置。为STEP 7-Micro/WIN设置波特率和站地址您必须为STEP 7-Micro/WIN配置波特率和站地址。其波特率必须与网络上其它设备的波特率一致，而且站地址必须唯一。通常，您不需要改变STEP 7-Micro/WIN的缺省站地址0。如果网络上还含有其它编程工具包，那么您可能需要改动STEP 7-Micro/WIN的站地址。表7-2 S7-200设备的缺省站地址S7-200设备缺省地址STEP 7-Micro/WIN0HMI（TD200、TP或OP）1S7-200 CPU2如图7-3所示，为STEP 7-Micro/WIN配置波特率和站地址非常简单。在操作栏中点击通讯图标，然后执行以下步骤：1. 在通讯设置窗口中双击图标。2. 在Set PG/PC Interface对话框中点击属性按钮。3. 为STEP 7-Micro/WIN选择站地址。4. 为STEP 7-Micro/WIN选择波特率。为S7-200设置波特率和站地址您也必须为S7-200配置波特率和站地址。S7-200的波特率和站地址存储在系统块中。在为S7-200设置了参数之后，您必须将系统块下载至S7-200中。每一个S7-200通讯口的波特率缺省设置为9.6k，站地址的缺省设置为2。如图7-4所示，使用STEP 7-Micro/WIN为S7-200设置波特率和站地址。您可以在操作栏中点击系统块图标或者在命令菜单中选择View Component System Block，然后执行以下步骤：1. 为S7-200选择站地址。2. 为S7-200选择波特率。3. 下载系统块到S7-200。提示可以选择各种波特率。在下载系统块期间，STEP 7-Micro/WIN将会验证所选的波特率。如果选定的波特率可能会妨碍STEP 7-Micro/WIN与其它S7-200进行通讯，那么它将不被下载。设置远端地址在将新设置下载到S 7 - 2 0 0 之前， 您必须为STEP 7-Micro/WIN（本地）的通讯（COM）口和S7- 200（远端） 的地址作配置，使它与远端的S7-200的当前设置相匹配。如图7-5所示。在下载了新设置后，您可能需要重新配置PG/PC接口波特率设置（如果新设置与远端S7-200 的设置不同）。关于波特率的配置，可参考图7-3。图7-5 配置STEP 7-Micro/WIN在网络上寻找S7-200 CPU您可以寻找并且识别连接在网络上的S7-200。在搜索S7-200时，您也可以寻找特定波特率上的网络或所有波特率上的网络。只有在使用PPI多主站电缆时，才能实现全波特率搜索。若在使用CP卡进行通讯的情况下，该功能将无法实现。搜寻从当前选择的波特率开始。1. 打开通讯对话框并双击刷新图标开始搜寻。2. 要使用所有波特率搜寻，选中在所有波特率下搜寻复选框。为网络选择通讯协议下面是S7-200 CPU所支持的协议的总览。1. 点对点接口（PPI）2. 多点接口（MPI）3. 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