VersaPro & GE 90-30

There is an instruction, MCR, that I believe when conditions in front of it are "true" then the rungs between the MCR and ENDMCR are scanned but remain at last state....ie doesnt allow any output changes. Am I reading this correct?

Not quite Ron,

Within an MCR zone, when the MCR instruction is TRUE, all rungs are scanned, but all coils are turned off. When the MCR instruction goes FALSE, the rungs in the zone are handled normally.

If, instead of the MCR/ENDMCR pair of instructions, you use the JUMP/LABEL pair, the coils between the JUMP and the LABEL will be frozen in their last state. The rungs are skipped.

There is no instruction in the Series 90 function set that sets up a zone where the rungs are scanned, but the coil states are frozen. MCR scans the rungs but turns off the coils. JUMP freezes the coils because it doesn't scan the rungs.

Thanks Steve, thats what I hoping the books said but wasnt sure. I think I need the instruction to turn the outputs off.

An example and see if you think it is prudent. I have a system I will have an ESTOP input from, if I want the program to turn the outputs OFF when the ESTOP is NOT healthy then I should use the appropriate input from the ESTOP ckt into the MCR, and use ENDMCR at end of program?

Naturally I will disable the output power from the plc via the estop but this is a redundant feature I would like to incorporate.

If you put all the outputs that you want to be turned off within the MCR zone controlled by the ESTop input you'll get that results you want. Be aware that the MCR will not unlatch latch instructions.

The only drawback that I can see to using MCR zones is in troubleshooting. You could be using VersaPro or Logicmaster to monitor the program and the logic in a rung could show as true, but the coil instruction would show as being off, causing all sorts of confusion. Creating a conditional zone can be easier than putting an EStop contact in every rung with an output, but with the contact instruction, you can see why the coil is off.

Logicmaster software shows a double left-hand rail between the MCR and the ENDMCR to indicate a conditional zone. VersaPro doesn't give you any such cues.

thanks, glad you said that, I have already started creating the ladder using a ESTOP is good contact. Asked because I thought this may be another way. I also thought the use of a contact representing ESTOP good would be easier to understand for troubleshooting.

Its been awhile since I have actually programmed a machine from start to scratch, I normally just add logic here and there for alarms or troubleshoot using codes. I have a small simple project now with an L sealer that my brain is refusing to cooperate on. I have written a start point but there are some issues I have to iron out, mainly auto cylce and cycle once.

I am using VersaPro.