Rockwell MAJ execution question

[BAJ]

In the past if I needed to change the jog speed every scan I used two identical MAJ blocks with a toggle bit to switch which one is "on" and which one is resetting every-other scan to satisfy the off-to-on edge triggering of the MAJ.

I just came across someone else's code and see they are doing an unlatch coil (OTU) of the MAJ Motion Control instance variable ".EN" right before calling the MAJ - does this work to create the edge trigger? It would be cleaner than my way if it does.

It's been my understanding the MAJ block needs to be solved with the input pin false to see the edge transition.

I only have access to the offline copy of the program and no motion axis to test with in my office. Any input will be appreciated.

Thanks,
-Brad

 

[Phrog30]

Best practice is to never manipulate the status bits on motion instructions. Let them do their work.

 

[DaveW]

Try using the instruction Motion Change Dynamics (MCD) to change speed on the fly.

 

[kamenges]

DaveW, I believe the MCD instruction is edge triggered as well so it would suffer from the same limitation as the MAJ in this case. You could build a sequencer that cycled between two MAJs to the same axis or between an MAJ and an MCD to satisfy the alternate scan issue.

I have programmed several closed loop tension axes using Rockwell motion and have used the OTU of the EN of a jog to allow updates every scan. I have never run across any issues with this.

Keith

 

[BAJ]

DaveW, I believe the MCD instruction is edge triggered as well so it would suffer from the same limitation as the MAJ in this case. You could build a sequencer that cycled between two MAJs to the same axis or between an MAJ and an MCD to satisfy the alternate scan issue.

I have programmed several closed loop tension axes using Rockwell motion and have used the OTU of the EN of a jog to allow updates every scan. I have never run across any issues with this.

Keith

Thanks Keith, my thoughts exactly. Thanks for confirming the OTU works.