RSLogix 5000 Add-On Instruction Library

Donald Zoricak from the Baton Rouge office created a library of commonly needed add-on instructions that can be used in RSLogix 5000 for both CompactLogix and ControlLogix PLCs that are not included in Rockwell’s default instruction set. These functions are useful for a wide variety of applications involving communication checks between devices, first out logic, or voting logic between multiple Boolean inputs:

Trigger an output based on a settable number of inputs being triggered. This add-on is used in shutdown logic for voting based trips or monitoring multiple conditions to trigger sequence steps.

Check communication status between two devices. This logic is used to monitor a Boolean (heartbeat based) or an integer value (clock based) to determine if the value has changed in a configurable amount of time. This value is typically linked to a value that is programmed to change being read frequently from a remote device through a communication link.

Determine the first Boolean input to trigger out of a set and latch the value until it is reset. This logic is useful in situations where multiple alarms or shutdown conditions can occur simultaneously. All signals can be monitored by this block to determine the first condition for troubleshooting and finding root causes.

Timer based add-on instructions. These instructions include a Heartbeat generator which pairs well with the communication check instructions, a pulse timer which allows the programmer to configure a pulse on-time and off-time for a Boolean output, and timer converter instructions.

These instructions are not just limited to the cases illustrated above and can be used and various other ways. Past projects have required similar functionality, but now we have a concise and proven way to implement these functions into future projects without repeating what already has been done.

The RSLogix 5000 Add-On Instruction Library can be found on the SharePoint engineering site under templates or by clicking the following link.

Thanks, Don, for your contribution!

If you have created any utilities (not just related to programming), email Joe Driver to have it uploaded to SharePoint and it may be featured in a future spotlight.

Please continue to contribute to the Technical Community Toolbox on SharePoint, and offer your support and input to Joe as he helps us move forward with this important endeavor.