PLC5/30 Oddity Jumping without JMP

I have a lot of experience on SLC500's and now have to troubleshoot a few PLC5's. I picked up on most of the operation, but one of the 5's (running a plating line) has an oddity I haven't figured out & was wondering if someone could shed some light on.

This is a PLC5/30 with 6 racks, consiting of 4 ladder files - but nowhere in ladder 2 is there a JMP or JSR command, so how is the PLC going to the other 3 ladders (they ARE being processed or the line wouldn't run) All the other PLC5's use JMP's for other ladders.

Is there some other way? I have attached a ZIP of ladder 2.

OK, I've looked at your program.

I even added instructions to rungs 3,4,7 to see if they ran.

I ran it with RSLogix Emulate5, and it doesn't appear that those ladders are executing. I would check again to see if they really are executing before doing anyting else.

MCP status, overview
This is from RsLogix5 help.
This should explain whats going on
Mickey



The SoftLogix 5 and certain PLC-5 processors have the capability of running 16 main control programs (A-P). This status tab contains information identifying the file numbers for the MCP programs and which programs are disabled. (These options are not available with all processors). By using an MCP for each machine or function of your process, you separate SFC from ladder logic, modularizing processes and facilitating troubleshooting. MCPs may be any mix of SFC or ladder files.

Fields on this display that are in gray are read-only. Fields shown in white are read/write. However, this information is seldom written to by the user program or programming device (unless you want to reset or clear a function). If you write to status file data, make sure that you first understand the function fully.
This information appears on the MCP tab with the Structured Radix selected.
Access this dialog by double-clicking the Processor Status icon in the project tree or double-clicking the status (S2) file. Then click the MCP tab to give it focus.

Click here for a list of the fields on the dialog and their definitions.



What do you want to do?

Specify the order of your (MCP) Main Control Programs
Clear minor error
Clear major error
Learn about the radix, properties, and usage buttons

Rockwell Software Inc., 1997, 1998, 1999, 2000

Thanks Mickey

I just checked that programs status & all the ladders are listed under the MCP tab, I also checked some of the other programs I have to work on (with JSR's) & found 1 that has both JSR U:3 in ladder 2 AND ladders 2 & 3 listed under MCP - does this mean it processes ladder 3 twice every loop?
(Could be unpredictable or dangerous if it is)

Yes, I think it would if there are no condition in front of to JSR.

Mickey