外文文獻(xiàn)及翻譯--理解s7--200網(wǎng)絡(luò)通訊的基本概念

1、<p><b>　　中文3186字</b></p><p><b>　　中文譯文</b></p><p>　　理解S7--200網(wǎng)絡(luò)通訊的基本概念</p><p><b>　　為網(wǎng)絡(luò)選擇通訊接口</b></p><p>　　S7--200可以滿足您的通訊和網(wǎng)絡(luò)需求，它

2、不僅支持簡單的網(wǎng)絡(luò)，而且支持比較復(fù)雜的網(wǎng)絡(luò)。S7--200提供了通訊手段，使您可以用它與那些使用自己的通訊協(xié)議的設(shè)備，例如：打印機和稱重天平等進(jìn)行通訊。</p><p>　　S7--200可以支持各種類型的通訊網(wǎng)絡(luò)。在SET PG/PC Interface屬性對話框中進(jìn)行網(wǎng)絡(luò)選擇。一個選定的網(wǎng)絡(luò)將被作為一個接口來使用。能夠訪問這些通訊網(wǎng)絡(luò)的各類接口包括：</p><p>　　1.多主站PP

3、I電纜</p><p><b>　　2.CP通訊卡</b></p><p><b>　　3.以太網(wǎng)通訊卡</b></p><p>　　通過下列步驟，您可以為STEP 7--Micro/WIN選擇通訊接口。參見圖7-1。</p><p>　　1. 在通訊設(shè)置窗口中雙擊圖標(biāo)。</p>&l

4、t;p>　　2. 為STEP 7--Micro/WIN選擇接口參數(shù)。</p><p>　　圖7-1 STEP 7--Micro/WIN通訊接口</p><p><b>　　多主站PPI電纜</b></p><p>　　S7--200可以通過兩種不同類型的PPI多主站電纜進(jìn)行通訊。這些電纜允許通過RS--232或USB接口進(jìn)行通訊。<

5、/p><p>　　如圖7-2所示，選擇PPI多主站電纜的方法很簡單。只需執(zhí)行以下步驟即可：</p><p>　　1. 在Set PG/PC Interface屬性頁中，點擊屬性按鈕。</p><p>　　2. 在屬性頁中，點擊本地連接標(biāo)簽。</p><p>　　3. 選中USB或所需的COM端口。</p><p>　　圖7

6、-2 PPI多主站電纜選擇</p><p><b>　　提示</b></p><p>　　請注意，一次只能使用一個USB接口。</p><p><b>　　提示</b></p><p>　　本手冊的實例使用的是RS--232/PPI多主站電纜。原先的PC/PPI電纜已RS--232/PPI多主站電纜

7、替代。另外，USB/PPI電纜也適用于這些實例。關(guān)于這些電纜的訂貨號，可參見附錄C。</p><p>　　在PROFIBUS網(wǎng)絡(luò)上使用主站和從站器件。</p><p>　　S7--200支持主--從網(wǎng)絡(luò)，并能在PROFIBUS網(wǎng)絡(luò)中充當(dāng)主站或從站，而STEP 7--Micro/WIN只能作為主站。</p><p><b>　　主站</b><

8、;/p><p>　　網(wǎng)絡(luò)上的主站器件可以向網(wǎng)絡(luò)上的其它器件發(fā)出要求。主站也可以對網(wǎng)絡(luò)上其它主站的要求作出響應(yīng)。典型的主站器件包括：STEP 7--Micro/WIN、TD200等HMI產(chǎn)品和S7--300或S7--400 PLC。在向其它S7--200發(fā)出請求以獲取信息（點對點通訊）時，S7--200是作為主站的。</p><p><b>　　提示</b></p&g

9、t;<p>　　如果網(wǎng)絡(luò)上有其它主站，TP070將無法工作。</p><p><b>　　從站</b></p><p>　　配置為從站的器件只能對其它主站的要求作出響應(yīng)，自己不能發(fā)出要求。對于多數(shù)情況，S7--200被配置為從站。作為從站，S7--200響應(yīng)主站的要求。作為從站時，S7--200將負(fù)責(zé)響應(yīng)來自某網(wǎng)絡(luò)主站器件（如操作員面板或STEP 7--

10、Micro/WIN）的請求。</p><p><b>　　設(shè)置波特率和站地址</b></p><p>　　數(shù)據(jù)通過網(wǎng)絡(luò)傳輸?shù)乃俣仁遣ㄌ芈?。其單位通常為Kbaud或者M(jìn)baud。波特率用于量度在給定時間內(nèi)傳輸數(shù)據(jù)的多少。比如，19.2k的波特率即表示傳輸速率為每秒19200比特。在同一個網(wǎng)絡(luò)中通訊的器件必須被配置成相同的波特率。因此，網(wǎng)絡(luò)的最高波特率取決于連接在該網(wǎng)絡(luò)上

11、的波特率最低的設(shè)備。表7-1中列出了S7--200支持的波特率。</p><p>　　表7-1 S7--200支持的波特率</p><p>　　在網(wǎng)絡(luò)中要為每個設(shè)備指定唯一的站地址。唯一的站地址可以確保數(shù)據(jù)發(fā)送到正確的設(shè)備或者來自正確的設(shè)備。S7--200支持的網(wǎng)絡(luò)地址為從0到126。如果某S7--200帶有兩個端口，那么每個端口都會有一個網(wǎng)絡(luò)地址。表7-2列出了S7--200設(shè)備的缺?。?/p>

12、工廠）設(shè)置。</p><p>　　表7-2 S7--200設(shè)備的缺省站地址</p><p>　　為STEP 7--Micro/WIN設(shè)置波特率和站地址</p><p>　　您必須為STEP 7--Micro/WIN配置波特率和站地址。其波特率必須與網(wǎng)絡(luò)上其它設(shè)備的波特率一致，而且站地址必須唯一。</p><p>　　通常，您不需要改變STEP

13、 7--Micro/WIN的缺省站地址0。如果網(wǎng)絡(luò)上還含有其它編程工具包，那么您可能需要改動STEP 7--Micro/WIN的站地址。</p><p>　　如圖7-3所示，為STEP 7--Micro/WIN配置波特率和站地址非常簡單。在操作欄中點擊通訊圖標(biāo)，然后執(zhí)行以下步驟：</p><p>　　圖7-3 配置STEP 7--Micro/WIN</p><p>

14、　　1. 在通訊設(shè)置窗口中雙擊圖標(biāo)。</p><p>　　2. 在Set PG/PC Interface對話框中點擊屬性按鈕。</p><p>　　3. 為STEP 7--Micro/WIN選擇站地址。</p><p>　　4. 為STEP 7--Micro/WIN選擇波特率。</p><p>　　為S7--200設(shè)置波特率和站地址</

15、p><p>　　您也必須為S7--200配置波特率和站地址。S7--200的波特率和站地址存儲在系統(tǒng)塊中。在為S7--200設(shè)置了參數(shù)之后，您必須將系統(tǒng)塊下載至S7--200中。每一個S7--200通訊口的波特率缺省設(shè)置為9.6k，站地址的缺省設(shè)置為2。</p><p>　　如圖7-4所示，使用STEP 7--Micro/WIN為S7--200設(shè)置波特率和站地址。您可以在操作欄中點擊系統(tǒng)塊圖標(biāo)

16、或者在命令菜單中選擇View > Component >System Block，然后執(zhí)行以下步驟：</p><p>　　1. 為S7--200選擇站地址。</p><p>　　2. 為S7--200選擇波特率。</p><p>　　3. 下載系統(tǒng)塊到S7--200。</p><p>　　圖7-4 配置S7-200 CPU<

17、/p><p><b>　　提示</b></p><p>　　可以選擇各種波特率。在下載系統(tǒng)塊期間，STEP 7--Micro/WIN將會驗證所選的波特率。如果選定的波特率可能會妨礙STEP 7--Micro/WIN與其它S7--200進(jìn)行通訊，那么它將不被下載。</p><p><b>　　設(shè)置遠(yuǎn)端地址</b></p&g

18、t;<p>　　在將新設(shè)置下載到S 7 -- 2 0 0 之前， 您必須為STEP 7--Micro/WIN（本地）的通訊（COM）口和S7-- 200（遠(yuǎn)端） 的地址作配置，使它與遠(yuǎn)端的S7--200的當(dāng)前設(shè)置相匹配。如圖7-5所示。</p><p>　　在下載了新設(shè)置后，您可能需要重新配置PG/PC接口波特率設(shè)置（如果新設(shè)置與遠(yuǎn)端S7--200 的設(shè)置不同）。關(guān)于波特率的配置，可參考圖7-3。&

19、lt;/p><p>　　圖7-5 配置STEP 7--Micro/WIN</p><p>　　在網(wǎng)絡(luò)上尋找S7--200 CPU</p><p>　　您可以尋找并且識別連接在網(wǎng)絡(luò)上的S7--200。在搜索S7--200時，您也可以尋找特定波特率上的網(wǎng)絡(luò)或所有波特率上的網(wǎng)絡(luò)。</p><p>　　只有在使用PPI多主站電纜時，才能實現(xiàn)全波特率搜索。

20、若在使用CP卡進(jìn)行通訊的情況下，該功能將無法實現(xiàn)。搜尋從當(dāng)前選擇的波特率開始。</p><p>　　1. 打開通訊對話框并雙擊刷新圖標(biāo)開始搜尋。</p><p>　　2. 要使用所有波特率搜尋，選中在所有波特率下搜尋復(fù)選框。</p><p><b>　　為網(wǎng)絡(luò)選擇通訊協(xié)議</b></p><p>　　下面是S7--200

21、 CPU所支持的協(xié)議的總覽。</p><p>　　1. 點對點接口（PPI）</p><p>　　2. 多點接口（MPI）</p><p>　　3. PROFIBUS</p><p>　　圖7-6 搜索網(wǎng)絡(luò)上的CPU</p><p>　　在開放系統(tǒng)互聯(lián)（OSI）七層模式通訊結(jié)構(gòu)的基礎(chǔ)上，這些通訊協(xié)議在一個令牌環(huán)網(wǎng)絡(luò)上實

22、現(xiàn)。令牌環(huán)網(wǎng)絡(luò)符合歐洲標(biāo)準(zhǔn)EN 50170中定義的PROFIBUS標(biāo)準(zhǔn)。這些協(xié)議是非同步的字符協(xié)議，有1位起始位、8位數(shù)據(jù)位、偶校驗位和1位停止位。通訊結(jié)構(gòu)依賴于特定的起始字符和停止字符、源和目的站地址，報文長度和數(shù)據(jù)校驗和。在波特率一致的情況下，這些協(xié)議可以同時在一個網(wǎng)絡(luò)上運行，并且互不干擾。如果帶有擴展模塊CP243--1和CP243--1 IT，那么S7--200也能運行在以太網(wǎng)上。</p><p><

23、;b>　　PPI協(xié)議</b></p><p>　　PPI是一種主--從協(xié)議：主站器件發(fā)送要求到從站器件，從站器件響應(yīng)，參見圖7-7。從站器件不發(fā)信息，只是等待主站的要求并對要求作出響應(yīng)。</p><p>　　主站靠一個PPI協(xié)議管理的共享連接來與從站通訊。PPI并不限制與任意一個從站通訊的主站數(shù)量，但是在一個網(wǎng)絡(luò)中，主站的個數(shù)不能超過32。</p><

24、p>　　圖7-7 PPI 網(wǎng)絡(luò)</p><p>　　如果在用戶程序中使能PPI主站模式，S7--200 CPU在運行模式下可以作主站。（參見附錄B中SMB30的描述）在使能PPI主站模式之后，可以使用網(wǎng)絡(luò)讀寫指令來讀寫另外一個S7--200。當(dāng)S7--200作PPI主站時，它仍然可以作為從站響應(yīng)其它主站的請求。</p><p>　　PPI高級允許網(wǎng)絡(luò)設(shè)備建立一個設(shè)備與設(shè)備之間的邏輯連

25、接。對于PPI高級，每個設(shè)備的連接個數(shù)是有限制的。S7--200支持的連接個數(shù)如表7-3所示。所有的S7--200 CPU都支持PPI和PPI高級協(xié)議，而EM277模塊僅僅支持PPI高級協(xié)議。</p><p>　　表7-3 S7--200 CPU和EM277模塊的連接個數(shù)模塊波特率連接數(shù)</p><p>　　表7-3 S7--200 CPU和EM277模塊的連接個數(shù)</p>

26、<p><b>　　MPI協(xié)議</b></p><p>　　MPI允許主--主通訊和主--從通訊，參見圖7-8。與一個S7--200 CPU通訊，STEP 7--Micro/WIN建立主--從連接。MPI協(xié)議不能與作為主站的S7--200 CPU通訊。</p><p>　　網(wǎng)絡(luò)設(shè)備通過任意兩個設(shè)備之間的連接通訊（由MPI協(xié)議管理）。設(shè)備之間通訊連接的個數(shù)受S

27、7--200CPU或者EM277模塊所支持的連接個數(shù)的限制。S7--200支持的連接個數(shù)如表7-3所示。</p><p>　　對于MPI協(xié)議，S7--300和S7--400 PLC可以用XGET和XPUT指令來讀寫S7--200的數(shù)據(jù)。要得到更多關(guān)于這些指令的信息，參見S7--300或者S7--400的編程手冊。</p><p>　　圖7-8 MPI網(wǎng)絡(luò)</p><p&

28、gt;　　PROFIBUS協(xié)議</p><p>　　PROFIBUS協(xié)議通常用于實現(xiàn)與分布式I/O（遠(yuǎn)程I/O）的高速通訊?？梢允褂貌煌瑥S家的PROFIBUS設(shè)備。這些設(shè)備包括簡單的輸入或輸出模塊、電機控制器和PLC。</p><p>　　PROFIBUS網(wǎng)絡(luò)通常有一個主站和若干個I/O從站，參見圖7-9。主站器件通過配置可以知道I/O從站的類型和站號。主站初始化網(wǎng)絡(luò)使網(wǎng)絡(luò)上的從站器件與配

29、置相匹配。主站不斷地讀寫從站的數(shù)據(jù)。圖7-9 PROFIBUS網(wǎng)絡(luò)。</p><p>　　圖7-9 PROFIBUS網(wǎng)絡(luò)</p><p>　　當(dāng)一個DP主站成功配置了一個DP從站之后，它就擁有了這個從站器件。如果在網(wǎng)上有第二個主站器件，那么它對第一個主站的從站的訪問將會受到限制。</p><p><b>　　TCP/IP協(xié)議</b></p

30、><p>　　通過以太網(wǎng)擴展模塊（CP243--1）或互聯(lián)網(wǎng)擴展模塊（CP243--1 IT），S7--200將能支持TCP/IP以太網(wǎng)通訊。表7-4列出了這些模塊所支持的波特率和連接數(shù)。</p><p>　　表7-4 以太網(wǎng)模塊（CP243--1）和互聯(lián)網(wǎng)模塊（CP243--1 IT）的連接數(shù)。</p><p>　　表7-4 以太網(wǎng)模塊（CP243--1）和互聯(lián)網(wǎng)模塊

31、（CP243--1 IT）的連接數(shù)</p><p>　　若需更多信息，可參考SIMATIC NET CP243--1工業(yè)以太網(wǎng)通訊處理器手冊或SIMATIC NETCP243--1 IT工業(yè)以太網(wǎng)及信息技術(shù)通訊處理器手冊。</p><p><b>　　英文資料原文</b></p><p>　　Understanding the Basics o

32、f S7-200 Network Communications</p><p>　　Selecting the Communication Interface for Your Network</p><p>　　by Moniruzzaman, Mohammad.; M.A.Sc.; Concordia University (Canada).; 2006;</p><

33、;p>　　The 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

34、 communicate with other devices, such as printers and weigh scales which use their own communications protocols.</p><p>　　The S7-200 supports many different types of communication networks. The selection of

35、a network is performed 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:</p>

36、<p>　　1. PPI Multi-Master cables</p><p>　　2. CP communication cards</p><p>　　3. Ethernet communication cards</p><p>　　To select the communication interface for STEP 7--Micro/W

37、IN, you perform the following steps. See Figure 7-1.</p><p>　　1. Double-click the icon in the Communications Setup window.</p><p>　　2. Select the interface parameter for</p><p>　　Fi

38、gure 7-1 STEP 7--Micro/WIN Communications Interface</p><p>　　PPI Multi-Master Cables</p><p>　　The S7-200 supports communication through two different types of PPI Multi-Master cables. These cabl

39、e types permit communication through either an RS-232 or a USB interface.</p><p>　　As shown in Figure 7-2, selecting the PPI Multi-Master cable type is simple. You perform the following steps:</p><

40、;p>　　1. Click the Properties button on the Set PG/PC Interface property page.</p><p>　　2. Click the Local Connection tab on the Properties page.</p><p>　　3. Select the USB or the desired COM

41、port.</p><p>　　Figure 7-2 PPI Multi-Master Cable Selection</p><p><b>　　Tip</b></p><p>　　Please note that only one USB cable can be used at a time.</p><p>&l

42、t;b>　　Tip</b></p><p>　　Examples 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 avail

43、able. Refer to Appendix E for order numbers.</p><p>　　Using Master and Slave Devices on a PROFIBUS Network</p><p>　　The S7-200 supports a master-slave network and can function as either a master

44、 or a slave in a PROFIBUS network, while STEP 7--Micro/WIN is always a master.</p><p><b>　　Masters</b></p><p>　　A device that is a master on a network can initiate a request to anoth

45、er 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

46、PLCs. The S7-200 functions as a master when it is requesting information from another S7-200 (peer-to-peer communications).</p><p><b>　　Tip</b></p><p>　　A TP070 will not work on a ne

47、twork with another master device.</p><p><b>　　Slaves</b></p><p>　　A device that is configured as a slave can only respond to requests from a master device; a slave never initiates a

48、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.</p><p>　　Setting

49、the Baud Rate and Network Address</p><p>　　The speed that data is transmitted across the network is the baud rate, which is typically measured in units of kilo baud (kbaud) or mega baud (Mbaud). The baud rat

50、e 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.</p><p>　　Every device that communica

51、tes 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

52、rates supported by the S7-200.</p><p>　　Table 7-1 Baud Rates Supported by the S7-200</p><p>　　The network address is a unique number that you assign to each device on the network. The unique net

53、work 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 lis

54、ts the default (factory) settings for the S7-200 devices.</p><p>　　Table 7-2 Default Addresses for S7-200 Devices</p><p>　　Setting the Baud Rate and Network Address for STEP 7--Micro/WIN</p&g

55、t;<p>　　You 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. </p><p>

56、　　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.</p><p>

57、　　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:</p><p>

58、;　　1. Double-click the icon in the Communications Setup window.</p><p>　　2. Click the Properties button on the Set PG/PC Interface dialog box.</p><p>　　3. Select the network address for STEP 7--

59、Micro/WIN.</p><p>　　4. Select the baud rate for STEP 7--Micro/WIN.</p><p>　　Figure 7-3 Configuring STEP 7--Micro/WIN</p><p>　　Setting the Baud Rate and Network Address for the S7-20

60、0</p><p>　　You 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, y

61、ou must download the system block to the S7-200.</p><p>　　The default baud rate for each S7-200 port is 9.6 kbaud, and the default network address is 2.</p><p>　　As shown in Figure 7-4, use STEP

62、 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 follow

63、ing steps:</p><p>　　1. Select the network address for the S7-200.</p><p>　　2. Select the baud rate for the S7-200.</p><p>　　3. Download the system block to the S7-200.</p>&l

64、t;p>　　Figure 7-4 Configuring the S7-200 CPU</p><p><b>　　Tip</b></p><p>　　Selection of all baud rate options is permitted. STEP 7--Micro/WIN validates this selection during the dow

65、nload 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.</p><p>　　Setting the Remote Address</p><

66、;p>　　Before 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

67、remote S7-200. See Figure 7-5.</p><p>　　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

68、remote S7-200). Refer to Figure 7-3 to configure the baud rate.</p><p>　　Figure 7-5 Configuring STEP 7--Micro/WIN</p><p>　　Searching for the S7-200 CPUs on a Network</p><p>　　You ca

69、n 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.</p><p>　　Only PPI Multi-Mas

70、ter 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.</p><p>　　1. Open the Communicat

71、ions dialog box and double-click the Refresh icon to start the search.</p><p>　　2. To search all baud rates, select the Search All Baud Rates check box. 2.</p><p>　　Selecting the Communications

72、Protocol for Your Network</p><p>　　The following information is an overview of the protocols supported by the S7-200 CPUs.</p><p>　　1. Point-to-Point Interface (PPI)</p><p>　　2. Mul

73、ti-Point Interface (MPI)</p><p>　　3. PROFIBUS</p><p>　　Figure 7-6 Searching for CPUs on a Network</p><p>　　Based on the Open System Interconnection (OSI) seven-layer model of commun

74、ications 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 proto

75、cols 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 ch</p>&l

76、t;p>　　Ethernet is also available for the S7-200 CPU with expansion modules CP243--1 and CP243--1 IT.</p><p>　　PPI Protocol</p><p>　　PPI is a master-slave protocol: the master devices send req

77、uests 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.</p><p>　　Masters

78、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 maste

79、rs on the network.</p><p>　　Figure 7-7 PPI Network</p><p>　　S7-200 CPUs can act as master devices while they are in RUN mode, if you enable PPI master mode in the user program. (See the descript

80、ion 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.</p><p>　　While the S7-200 is acting as a PP

81、I master, it still responds as a slave to requests from other masters.</p><p>　　PPI Advanced allows network devices to establish a logical connection between the devices. With PPI Advanced, there are a limit

82、ed number of connections supplied by each device. See Table 7-3 for the number of connections supported by the S7-200.</p><p>　　All S7-200 CPUs support both PPI and PPI Advanced protocols, while PPI Advanced

83、 is the only PPI protocol supported by the EM 277 module.</p><p>　　Table 7-3 Number of Connections for the S7-200 CPU and EM 277 Modules</p><p>　　MPI Protocol</p><p>　　MPI allows bo

84、th 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 operatin

85、g as a master.</p><p>　　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 connectio

86、ns supported by the S7-200 CPU or EM 277 modules. See Table 7-3 for the number of connections supported by the S7-200. </p><p>　　For MPI protocol, the S7-300 and S7-400 PLCs use the XGET and XPUT instructio

87、ns 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.</p><p>　　Figure 7-8 MPI Network</p><p>　　PROFIBUS Protoc

88、ol</p><p>　　The 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

89、 range from simple input or output modules to motor controllers and PLCs.</p><p>　　PROFIBUS networks typically have one master and several slave I/O devices. See Figure 7-9. The master device is configured t

90、o 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 da

91、ta to the slaves and reads input data from them.</p><p>　　Figure 7-9 PROFIBUS Network</p><p>　　When a DP master configures a slave device successfully, it then owns that slave device. If there i

92、s a second master device on the network, it has very limited access to the slaves owned by the first master.</p><p>　　TCP/IP Protocol</p><p>　　The S7-200 can support TCP/IP Ethernet communicatio

93、n 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.</p><p>　　Table 7-4 Number of Conne

94、ctions for the Ethernet (CP 243--1) and the Internet (CP 243--1 IT) Modules</p><p>　　Refer to the CP 243--1 Communications Processor for Industrial Ethernet Manual or the CP 243--1 IT Communications Processo