I/O tags

I/O tags read or write InTouch application data to or from an external source. External data includes input and output from programmable controllers, process computers, and network nodes. I/O tag data values are remotely accessed through the following protocols:

• Microsoft Dynamic Data Exchange (DDE)

• SuiteLink™

When the value of an I/O tag changes in run-time memory, the InTouch HMI updates the remote application. Conversely, I/O tag values in InTouch are updated whenever the values of corresponding data items change in a remote application.

The InTouch HMI provides four types of I/O tags based upon the process data associated with the tag. These four types of I/O tags are similar to memory tag types.

• I/O Discrete

  I/O discrete tags are associated with component process properties whose values are represented by two possible states such as:

  • 0 or 1

  • False or true

  • On or off

  • High or low

• I/O Integer (Analog)

  I/O integer tags can be assigned 32-bit signed-integers between -2,147,483,648 and 2,147,483,647.

• I/O Real (Analog)

  I/O real tags can be assigned floating decimal point numbers between -3.4 x 1038 and 3.4 x 1038. When two real tags values are compared, the difference of two real tag values should be greater than FLT_EPSILON (value 1.19209290E-07F, in decimal 0.0000001192092896). All I/O real tag floating point calculations are performed with 64-bit resolution, but the results are stored as 32-bit numbers. For more information about the maximum precision of I/O real numbers, see IEEE decimal units.

• I/O Message

  I/O message tags can be assigned text strings up to a maximum of 131 single-byte characters.