This property allows controlling writing feedback confirmation to I/O Tags. It applies only to readable I/O Tags, that is, I/O Tags whose AllowRead property is set to True. Through this property, reading I/O Tags that receive writings is quicker. This property contains the configuration options described on the next table.
Available options for the WriteFeedbackMode property
Option |
Description |
|---|---|
0 - wfWaitNextRead |
I/O Tag reading is performed normally on the next scan |
1 - wfImmediateReadAfterWrite |
After each writing, a confirmation reading is performed as soon as possible (default) |
2 - wfTrustWriteSuccess |
If this I/O Driver indicates a successful writing, the written value is directly assumed by the I/O Tag, without reading it from a device |
Applications created before this property existed assume the value 0 - wfWaitNextRead when loaded. Example:
Sub CommandButton1_Click()
Dim mode
mode = Application.GetObject("Driver1").WriteFeedbackMode
MsgBox mode
Select case mode
Case 0
MsgBox "Tag reading is performed on the next scan."
Case 1
MsgBox "After each writing, a confirmation _
reading is performed as soon as possible."
Case 2
MsgBox "If the driver indicates a writing success, _
the written value is assumed directly by the tag, _
without reading it from the PLC."
End Select
End Sub
NOTE |
When using mode 2 - wfTrustWriteSuccess, the timestamp and quality may be incorrect, since in a successful writing the value is assumed by the I/O Tag without searching for its timestamp and quality in the device. In addition, the assumed value itself may present a little deviation due to any kind of simplification in numbers that may occur in the I/O Driver or in the device. Also, note that some I/O Drivers or protocols may indicate success, even when writings fail. So, the other modes, 1 - wfImmediateReadAfterWrite or 0 - wfWaitNextRead, must be preferred when possible. |