I/O tags - processing a value acquired from the communication

An object of the I/O tag type allows configuring a sizeable quantity of parameters, which determine the procedure of processing of so-called "raw" value acquired from communication. This document describes in detail individual steps for each of the value types separately. The listed information can helpful during analysis and comparison of values with process level and for programmers and users of the D2000 KomAPI open interface.

Processing of a new value of the I/O tag is performed withing the call of PointNewValue call-back function of the D2000 KomAPI interface.

Value types of I/O tags in the D2000 system: DI, AI, CI, TIR, TIA, QI, TXTI, DOUT, AO, CO, TOR, TOA, TXTO.

DI value type

If the entered value is valid ("Valid" status bit is set) and the value is not a default one (the "Default" status bit is not set), the following will be performed:

The value is ignored if the I/O tag is in default value mode. For further information see the Default value chapter.

A value change check is carried out, comparing the value with the previous one. If a change has been detected, then the value is sent to the D2000 Server after processing the process alarms.

AI, CI value types

In the case of AI type, if the value is valid, the validity check of the number in the floating-point format is executed. If the number is not valid, then the invalid value is sent to the D2000 Server.

If the entered value is valid ("Valid" status bit is set) and the value is neither default (the "Default" status bit is not set) nor simulated, the following steps will be performed:

The value is ignored if the tag is in default value mode. For further information see the Default value chapter.

A value change check is carried out, comparing the value with the previous one. If a change has been detected, then the value is sent to the D2000 Server after processing the process alarms.

TIR, TIA value types

If the entered value is valid ("Valid" status bit is set) and the value is neither default (the "Default" status bit is not set) nor simulated, the following steps will be performed:

The value is ignored if the tag is in default value mode. For further information see the Default value chapter.

A value change check is carried out, comparing the value with the previous one. If a change has been detected, then the value is sent to the D2000 Server after processing the process alarms.

QI, TXTI value types

The value is ignored if the tag is in default value mode. For further information see the Default value chapter.

A value change check is carried out, comparing the value with the previous one. If a change has been detected, then the value is sent to the D2000 Server after processing the process alarms.

DOUT value type

The value is ignored if the tag is in default value mode. For further information see the Default value chapter.

A value change check is carried out, comparing the value with the previous one. If a change has been detected, then the value is sent to the D2000 Server after processing the process alarms.

AO, CO value types

If the value is valid, the following steps will be performed:

The value is ignored if the tag is in default value mode. For further information see the Default value chapter.

A value change check is carried out, comparing the value with the previous one. If a change has been detected, then the value is sent to the D2000 Server after processing the process alarms.

TOR, TOA value types

If the value is valid, the following steps will be performed:

The value is ignored if the tag is in default value mode. For further information see the Default value chapter.

A value change check is carried out, comparing the value with the previous one. If a change has been detected, then the value is sent to the D2000 Server after processing the process alarms.

TXTO value type

The value is ignored if the tag is in default value mode. For further information see the Default value chapter.

A value change check is carried out, comparing the value with the previous one. If a change has been detected, then the value is sent to the D2000 Server after processing the process alarms.

Value limits check

The check is also executed internally for CI and CO types in the floating-point form. Checking of limits is executed, to verify the validity of the condition:

VMin_Limit <= Min_Limit <= Max_Limit <= VMax_Limit

If not (wrong values of dynamic limits), the "LimitsProblem" limit flag is set, otherwise, processing of the hysteresis and setting of a particular limit flag will be executed.

Value change check

Value change check, that is comparing the value with the last value that was acquired from communication, is used to reduce the number of data changes that are sent from the communication process to the D2000 Server and from the D2000 Server to other client processes of the D2000 system, such as the D2000 HI process, fully in accordance with the DODM design. The check proceeds as follows:

If any of the condition mentioned above is met and the new value differs from the old one, then the new value is sent to the D2000 Server.

Default value

The default value is activated by:

All valid values acquired during communication with the device (station) are saved and in case of the cancellation of the default value (by the operator from the D2000 HI process or by means of disabling the Use default value option) they are immediately sent into the system.

All the abovementioned options are configured in the Default value tab of the I/O tag control window.

I/O tags
I/O tag - configuration window
Values of I/O tags