PERFORMING A CONTROL OPERATION WHICH DOES NOT IN FACT OCCUR.
When the tag is put into the control inhibit mode, writing to the Field element value is prohibited. If the system is configured in such a way that it does not give the operator any indication that the tag is in the control inhibit mode, the operator may assume that he is performing a control operation which does not, in fact, occur.
Configure the system in such a way that it provides a visual indication to the operator that a tag is in the control inhibit mode.
Failure to follow these instructions can result in death, serious injury, or equipment damage.
To provide a visual indication to the operator that a tag is in the control inhibit mode the following can be done:
Set any of the following Citect.ini parameters in such a way that control inhibit mode will be indicated by changing the background color or overlaying the numeric or text graphics objects and symbol set objects with a dithered pattern:
and set [Page]IgnoreValueQuality parameter to a value of 0 or 2.
Use the Control Mode element value (0 if the tag is not in the control inhibit mode or 1 otherwise)
Use the Field element quality Tag Status ControlInhibit bit (1 if the tag is in the control inhibit mode or 0 otherwise)
Control inhibit mode allows you to prohibit writing to the Field tag element. Setting a tag in Control inhibit mode is applied system wide. Writing to the Field element will be prohibited for each of the I/O Data Consumers.
Control inhibit mode is controlled by the “Control Mode” element which is described in the following table.
|Reference Syntax||CitectSCADAData type||Description|
|TagName.ControlMode||INT||Value of Control Mode element|
Allowed values are:
0 – Control inhibit mode is Off.
1 – Control inhibit mode is On.
Default value: 0.
|TagName.ControlMode.VT||TIMESTAMP||Timestamp of when the value last changed|
|TagName.ControlMode.Q||QUALITY||Quality. The Control Mode quality is QUAL_GOOD if the tag was put into the Control inhibit mode on the primary server and it was propagated to redundant servers. Otherwise the general quality status will be QUAL_UNCR and the extended susbstatus will be QE_NOT_REPLICATED to indicate that not every redundant server is aware of the fact that the tag is in Control inhibit mode.|
|TagName.ControlMode.QT||TIMESTAMP||Timestamp of when the quality last changed|
|TagName.ControlMode.T||TIMESTAMP||Time of when the tag was put in or out of the Control inhibit mode. (equal to 0 at start up)|
Note: The quality of tags referenced by items, ex. Tag1.v or Tag1.Field.t, is GOOD and its timestamps are 0 (INVALID TIMESTAMP). Therefore they give no visual indication of any not good quality, error or change in handling state such as control inhibit or override mode regardless of the setting used for the [Page] IgnoreValueQuality parameter.