General information about function blocks

Function block alarm detection

Some function blocks detect alarms based on the limit information you enter. The alarm detection capabilities vary with each function block. The Books Online information for each function block lists the configurable alarm limits for that block. The following limits are configurable in some function blocks:

  • High high (HI_HI_LIM)

  • High (HI_LIM)

  • Low low (LO_LO_LIM)

  • Low (LO_LIM)

  • Deviation high (DV_HI_LIM)

  • Deviation low (DV_LO_LIM)

You define the alarm priority, acknowledgment, and messaging information in Control Studio when you are configuring process control loops.

Some function blocks detect general block error information and set bitstring indicators to report the error. Block errors vary with each function block. The Books Online information for each function block lists the block errors for that block. The following block errors are supported in some function blocks:

  • Block configuration error — Cause varies by block

  • Input failure/process variable has Bad status — The source of the block's process variable is bad. Indicates a hardware failure, a non-existent Device Signal Tag (DST), or a Bad status on the SIMULATE parameter.

  • Local override — The block is in Local Override (LO) mode.

  • Other — Cause varies by block

  • Out of Service — The block is in Out of Service (OOS) mode.

  • Output failure — The output value is not valid.

  • Readback failed — The I/O readback failed.

  • Simulate active — Simulation is enabled and the block is using a simulated value in its execution.

You can use block error information to generate an alarm or send a message.

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