Concept DFB: is there a similar thing for RSLogix5000


Thread Starter

Dean Murray

Schneider's Concept Software for programming Quantum PLCs etc. has a concept of DFB (user defined function block) which can be used multiple times thoughout a program and if updated will update all instances.

Is there any way to do a similar thing within RSLogix5000??

James Ingraham

Sort of.

You can have a subroutine that can be called in multiple places. The subroutine can be written in ladder diagram, sequential function chart, or structured text. You can have input and return parameters, and changing the subroutine in one place changes all instances.

You cannot, however, extend the library of function blocks that can be added to function block diagrams. Rockwell has been promising user-defined function blocks for a while now, but I have no idea when it will actually happen.

-James Ingraham
Sage Automation, Inc.
If you are programming in Ladder, you can create a Task as a subroutine and then call it multiple times using the JSR instruction. You can pass
parameters into and out of the routine. One limitation is that such a task is only available to other tasks in the same Program. Check the
documentation for the JSR/SBR/RET instructions under the Help menu.

Ron Davis