Single Integer - Alarm on Each Bit

A common practice for PLC programming is to store alarm conditions as series of bits inside the PLC and expose them to the world as an integer value. Each bit is essentially a binary value. A series of 8 bits, for example, could be represented as an 8-bit integer. This integer value can be monitored by Ignition's OPC-UA server as an integer value as a tag. This tag can then have as many alarms as the integer has bits by monitoring the integer's bit state.

The following table shows binary and decimal equivalents:

Binary

Decimal

10001110

142

In this case the tag would be an integer with a value of 142. This tag would have eight alarms. Each one of these alarms become active in accordance with its Boolean value.

To create the alarms on an integer tag value

  1. Edit the tag that has an integer value.

  2. Create an alarm by selecting the Alarming tab and clicking the green plus sign + to add an alarm.

  3. Complete the appropriate properties, for example, enter the Name of the alarm.

  4. From the Mode section drop-down, select Bit State and enter a value for the Bit Position.

  5. Repeat the same process for the remainder of the bits.