_OPCGroup (OPC client)

For every group that is to be used in the OPC server, an internal data point of type _OPCGroup must be present. This data point must be created before the group is created in the server, i.e. before configuration of the first data point with an address contained in this group.

Table: data point elements of _OPCGroup

DP Element Type Description
Active bit Sets the status of the group to active (1) or inactive (0). No update is made to an inactive group, and no general query can be triggered on it. However, items in inactive groups can be written.
AllItemsInvalid bit The value is set by the driver, and only displayed. Set (TRUE) by the driver if all items in a group have the quality BAD or UNCERTAIN. If at least one item has the quality GOOD, this value is set to FALSE.
DataSourceDevice bit If this value is set to TRUE, general queries take place directly from the hardware and are not answered from the server cache.
DeathBand float [%]

Determines the dead band smoothing for analog items in the group. A value is smoothed (i.e. no update of the client takes place), if:

|lastValueinCache - currentValue |<DeathBand*

(EUHigh -EULow )

The values EUHigh and EULow are set by the server or configured over the CALL-R interface.

DeleteGroup bit If a value of 1 is written to this element, the corresponding group is deleted in the server. The associated data point is not deleted.
DpIds dyn. indentifier This field shows the DpIds of all data points contained in the group. The first entry in this list corresponds to the first entry in the list ItemIds.
EnableCallback bit If this value is set to 0, the group returns no more callbacks. However, the values in the server CACHE are kept updated. (This is also the difference to inactive status for a group. In this, the items contained in the group in the CACHE are also no longer updated by the periphery.)
GetIds bit When a value is written in this, it updates the data in the fields DpIds and ItemIds.
ItemIds dyn. text array All ItemIds contained in a group are displayed here. This value cannot be written by the user. NOTE: Items may only be defined once in a group!
Refresh bit A change of value in this field triggers a general query on all items in the group.
RefreshTimer uint [s] If no callback comes from the server for RefreshTimer seconds, this timer triggers a refresh for the group directly on the DEVICE. The value should therefore not be lower than that of UpdateRateAct.
UpdateRateAct uint [ms] Actual update rate guaranteed by the server. This field is set by the server as a response to an UpdateRateReq change and cannot be written by the user. New values will be sent by the server no faster than every UpdateRateAct ms. If value changes should occur at the periphery faster than every UpdateRateAct ms, the values between are lost.
UpdateRateReq uint [ms] The update rate requested by the server for the group in milliseconds.
retryCorruptItems bool If an OPC group cannot add an OPC item via AddItem() (the address is invalid and the item is "corrupt"), the group notes this item. The DPE "retryCorruptItem" is set and you can try to add an item later.
itemInsState dyn. text array

This data array shows if an item was successfully inserted to the group

  • x - insertion not successful

  • 1 - insertion successful

  • 0 - not inserted because currently not necessary. This only applies to non-permanent groups