MVME297-128模塊控制器
該操作由DriveWindow線程使用非活動項完成。7.1.4在線所有在線值（驅(qū)動器狀態(tài)刷新、項目集窗格中的在線項目等）的處理方式相同，但有幾個組，因此有幾個DriveOPC線程處理它們。驅(qū)動器狀態(tài)刷新、驅(qū)動器面板工具欄、監(jiān)視器以及項目集窗格中當(dāng)前可見的項目集都有活動組。當(dāng)前可見項目集以外的組未處于活動狀態(tài)。高級信息DriveWindow 2 10-23這些值由DriveOPC線程讀取，該線程還調(diào)用DriveWindow中的建議接收器。在advice接收器中，緩存值，并將消息發(fā)布到DriveWindow線程，然后由該線程繪制值。在線項目在活動組中處于活動狀態(tài)。7.1.5運行監(jiān)視器在其他方面，運行監(jiān)視器的處理方式與所有其他在線項目相同，但DriveWindow中有一個額外的測量緩沖區(qū)。高級信息10-24 DriveWindow 2 7.1.6暫停監(jiān)視器當(dāng)監(jiān)視器暫停時，數(shù)據(jù)仍會收集到測量緩沖區(qū)中，但在監(jiān)視器繼續(xù)運行之前，DriveWindow中的緩存不會更新。7.1.7寫入值始終寫入設(shè)備。寫入的值也被緩存，但質(zhì)量被標(biāo)記為不確定。DriveWindow會立即從設(shè)備中讀取值（如果可以讀取），因此很少看到不確定的質(zhì)量。然而，DriveOPC可能知道項目之間的某些連接（例如，控制和狀態(tài)項目），其中寫入一個項目也會更改另一個項目的值。DriveOPC在其緩存中進(jìn)行內(nèi)部更改，這也會導(dǎo)致其他項目的質(zhì)量不確定，但DriveWindow不會立即對其進(jìn)行讀取。下文中未顯示回讀，但其執(zhí)行方式與更新中的相同。7.1.8控制。本地項目控制。本地在DriveOPC中有特殊處理。請注意，并非所有驅(qū)動器都有此項。高級信息DriveWindow 2 10-25項目的目的是通過DriveWindow獲取和釋放控制。當(dāng)值ON寫入項目時，將采取控制。但是，許多驅(qū)動器都有一個看門狗，它要求在10秒內(nèi)刷新ON值，否則驅(qū)動器會出現(xiàn)故障，面板丟失。除了正常向項目寫入值外，DriveOPC在讀取項目時也會在內(nèi)部寫入ON值，邏輯如下：?從設(shè)備讀取項目（并緩存）。?如果讀取值為ON，并且自上次寫入ON值后已過0.5秒，則重新寫入值ON（并以不確定的質(zhì)量緩存）。由于DriveOPC在內(nèi)部讀取活動組中的周期性活動項目，因此只要在DriveWindow的項目集窗格中鎖定并使項目聯(lián)機(jī)，看門狗就可以保持活動狀態(tài)。但是，如果您要使用驅(qū)動器面板工具欄，當(dāng)控制被獲取時，它也會執(zhí)行同樣的操作，我們不建議將項目也放到項目集窗格中。
The operation is done by a DriveWindow thread using inactive items. 7.1.4 On-line All on-line values (drive status refresh, on-line items in the item sets pane, etc.) are handled the same way, but there are several groups and thus several DriveOPC threads handling them. There are active groups for the drive status refresh, the drive panel toolbar, the monitor, and for the item set currenlty visible in the item sets pane. Groups for other than the currently visible item set are not active. Advanced Information DriveWindow 2 10-23 The values are read by the DriveOPC thread, which also calls back the advise sink in DriveWindow. Within the advise sink, the values are cached, and a message is posted to a DriveWindow thread, which then draws the values. The on-line items are active in an active group. 7.1.5 Running Monitor A running monitor is otherwise handled the same way as all other on-line items, but there is an additional measuring buffer within DriveWindow. Advanced Information 10-24 DriveWindow 2 7.1.6 Paused Monitor While a monitor is paused, the data is still collected into the measuring buffer, but the cache within DriveWindow is not updated until the monitor is continued. 7.1.7 Writing Values are always written to the device. The written value is also cached, but quality is marked uncertain. DriveWindow reads immediately the value back (if it is readable) from the device, so the uncertain quality is rarely seen. However, DriveOPC may know some connections between items (control and status items, for example), in which writing an item also changes the value of another item. DriveOPC does the change internally in its cache, which causes the quality of the other item to be uncertain, too, but the immediate read-back by DriveWindow is not done for it. The read-back is not shown in the following, but it is done the same way as in update. 7.1.8 Control.Local The item Control.Local has a special handling within DriveOPC. Note that not all drives have this item. Advanced Information DriveWindow 2 10-25 Purpose of the item is to take and release control by DriveWindow. When the value ON is written to the item, control is taken. However, many drives have a watchdog, which requires the ON value to be refreshed within 10 seconds, otherwise the drive faults with panel loss. In addition to writing values normally to the item, DriveOPC internally also writes the ON value, when the item is read, with the following logic: ? The item is read from the device (and cached). ? If the read value is ON, and 0.5 seconds has elapsed since the ON value was written last time, value ON is re-written (and cached with quality uncertain). Because DriveOPC internally reads cyclically active items in an active group, a watchdog can be kept alive just by locking and putting the item on-line in the item sets pane in DriveWindow. However, if you are going to use the drive panel toolbar, which does the same thing when control is taken, we do not recommend putting the item on-line in the item sets pane, too.
