opc接口技術(編輯修改稿)

　

【文章內容簡介】 ms () client Call Reply server Group的同步讀 single Items的異步讀 AsyncRead() AsyncReadComplete() server Dim WithEvents MyGroup ... nrItems, ServerHandles, ServerErrors, TransactionID, CancelID Call Reply client Private Sub Mygroup_AsyncReadComplete ( ByVal TransactionID As Long, ByVal NumItems As Long, ClientHandles() As Long, ItemValues() As Variant, Qualities() As Long, TimeStamps() As Date, Errors() As Long) MsgBox (Async Read Complete) End Sub Asynchronous read separates Call and Reply. Call supplies the ServerHandles Reply returns the corresponding ClientHandles AsyncRead (source= device) AsyncReadComplete() server Call Reply client AsyncRead (source= cache) AsyncRead (source = device) Although the AsynchReadComplete carries the ClientHandle of each item, it does not tell which AsynchRead caused the AsynchReadComplete event to fire. Call and Reply are linked by the TransactionID: this ID is returned in AsynchReadComplete。 It can also be used to cancel the operation AsyncCancel () AsyncCancelComplete () Transaction ID Reading (by events) the OPC group Dim WithEvents MyGroup ... Private Sub MyGroup_DataChange( _ ByVal TransactionID As Long, _ ByVal NrItems As Long, _ ClientHandles() As Long, _ 39。 returned by the server to the client ItemValues() As Variant, _ Qualities() As Long, _ TimeStamps() As Date) Dim tItems As Integer For tItems = LBound(ClientHandles) To UBound(ClientHandles) 39。 index 1..n TextValue(tItems 1).Text = ItemValues(tItems) 39。 display TextTimeStamp(tItems 1).Text = DateAdd(h, 9, TimeStamps(tItems)) TextQuality(tItems 1).Text = Qualities(tItems) Next tItems End Sub This function is called each time an item in the group changes The ClientHandles (here: 5 and 6) identifies the variables, not the “fully qualified itemID” The values are displayed in the TextValue, TextTimeStamp and TextQuality fields. The refresh rate is given in the group definition. Groups Events Although transmission by groups is more efficient than AsyncRead, it can be improved by using Groups Events (Global Data Change) This event is fired whenever a variable of a group changes. If the group is subscribed also to a Group Event (DataChange), . if the group is declared WithEvents, then both Events will be fired. The application must sort out the groups and the items. GlobalDataChange Dim WithEvents MyGroups As OPCGroups ... Private Sub MyGroups_GlobalDataChange( ByVal TransactionID As Long, 39。 =0 if called by Refresh ByVal GroupHandle As Long, ByVal NumItems As Long, ClientHandles() As Long, 39。 identifies the items ItemValues() As Variant, 39。 value of the items Qualities() As Long, 39。 value of the items TimeStamps() As Date) 39。 timestamps of the items Select Case GroupHandle 39。 depending on the group ... Case 1 39。 treat group 1 Case 2 39。 treat group 2 The GlobalDataChange event is fired when any item in a group changed. (if Groups is also with events, the corresponding Group_DataChange will also be called) OPC DA: Server Events Dim WithEvents MyServer As OPCServer 39。 define the event .. .. Private Sub Myserver_ServerShutDown(ByVal Reason As String) MsgBox my OPC Server amp。 amp。 quit End Sub This event signals to the client that the server shut down. The client must declare its server ?WithEvents“ and provide the corresponding event Subroutine This should stop all actions, otherwise exceptions will occur. OPC 的斷開 Private Sub ServerShutdown Dim dummyServer As OPCServer Dim Servers As Variant 39。 this is an array of strings Dim tServers As Integer Set myGroup1 = Nothing 39。 create a dummy server object Set myGroups = Nothing 39。 returns all available servers 39。 delete this object (was created by New) Set MyServer = Nothing To speed up connection/disconnection, an OPC server remembers its groups and clients when a client disconnects. To do this, an OPC server initialises its structures with a client counter of 2, instead of 1. Therefore, it is imperative to shut down explicitly the server, otherwise links will subside (and you will have kill the server to clear them). OPC DA的類庫 The OPC DA specification is not formal, conformance can hardly be checked against this document. To ensure that the standard is observed, the OPC foundation distributes on its website the DLLs (, op_ps,…) that contain the type libraries to access the OPC server. The vendors are not pelled to implement all features. For instance, the description of the variables is seldom used. Calling unimplemented functions causes exceptions that must be caught in Visual Basic with On Error … statements. There exist three versions of DA, , and , that behave differently, however, older servers do not have a property indicating which version they support. OPC AE 接口標準 ? AE 相關 概念 ? AE的組態 ? AE的目的 ? AE 通信模式 ? 事件的種類 ? 報警的條件 ? 報警確認 AE 相關 概念 An event is a general change of state that is relevant to the OPC server. An event signal a change: 1) in the field device (production started) 2) in the OPC server (alarm acknowledged) 3) in the application (operator action) An alarm is a state of the process that requires attention and is relevant to the OPC server. An alarm is represented by an alarm condition, (or short: condition), a state machine