Block write configuration

Use the Block Write tab to configure one or more block write groups. A block write group is a set of items for which values will be written to the field device in a single transaction. Each block write group configured for this object can be named <Block Name.>.

Note: Transaction timeouts and access paths for block write groups are inherited from the block write groups configured in the source DIObjects. The item references for each attribute are not copied. Instead item references are resolved by the Primary and Backup DIObject data sources. If aliases are used, both source DIObjects must support the same set of alias names.

Only values that are new for the attribute since the last transaction are written to the field device. A block write transaction must be initiated from a user or script via the TransactionTrigger attribute. You cannot trigger another transaction if the previous transaction has not completed.

Partial writes are supported. However, the system does not offer roll-back functionality. In the case of a block write failure or transaction timeout, some values may have been successfully sent, but there is no way to undo the value changes. For items that have not yet been written to, the data quality is set to BAD.

Click the Copy Common Block Writes button to display a dialog box that shows the block write groups configured in the Primary DIObject (shown in the Configured in primary window) and the Backup DIObject (shown in the Configured in backup window), and those block write groups shared by the two DIObjects (shown in the Identically named window). Click OK to add the block write groups in the Identically named window to the Available block writes list on the Block Write tab.

Important! Only block write groups shared by the Primary and Backup DIObjects can be configured in the RedundantDIObject. If you include non-shared groups, the RedundantDIObject will be placed in Warning state, and you cannot deploy the object. If you configure non-shared groups in the RedundantDIObject first, you can add them to either DIObject source at a later time. You then must validate the RedundantDIObject to change it from Warning state to Good state.

To configure additional block write groups, click the Add ("+" sign) button to start filling in a new group. To delete a row from a list, select the row and then click the Delete ("X" sign) button.

To add attributes to the Associated attributes list, select a block write group and click either the Copy Attributes from Primary or Copy Attributes from Backup button. All configured attributes from the respective DIObject sources (specific to the selected Block Write) are added to the Associated attributes list.

To configure additional attributes for a block write group, use the Add ("+" sign) and Delete ("X" sign) buttons.

Valid characters for block write group and attribute names include all alphabetic characters (A-Z, a-z), and/or numeric digits (0-9), and/or the following special characters: the underscore (_), the dollar sign ($), and the pound sign (#). Spaces are not allowed.

Runtime object attributes allow you to monitor transaction errors and other diagnostic information.

Note: Although block writes are intended to be individual transactions, the actual communication with the field device is dependent on the number and type of attributes, and it may be necessary to send and receive multiple messages to and from the field device. In the case of a block write operation, the logic in the field device must not use the written values until the full write operation is completed.

Options are as follows. For more information about the attribute associated with each option, see the attributes table in RedundantDIObject attributes.

Available block write groups:

This list contains all of the defined block write groups.

Block Write (BlockWriteList attribute)

The list of names of all configured block write groups. When a set is made with new values, it should contain a unique name for the block write group, from which data will be received. Group names should be unique across ScanGroupList, BlockReadList and BlockWriteList.

Associated attributes for <block write group name>:

This list contains all of the attributes that are configured for the selected block write group.

Attribute (<Block Name.>ItemList attribute)

The tag name of an item in the field device.