Setting Breakpoints with an S7-300

How do I get the Breakpoint commands in the "Test" menu activated.

I'm Online

in "TEST" mode

The FC is written in IL (AWL) and the display mode is also set to IL

As far as I understand that ought to be all I need to do, but all the menu points are still greyed out.

Help!

Hi guys,

the German's beat you to it this time. For the benefit of anybody else with this problem in future, the problem was that I was trying to go in from the offline copy of the program. You have to switch to online mode in Simatic Manager and then open the online version of the program - as usual it's the little things that cause the problems!

However, I'm still only halfway there. I can set by breakpoint OK, but I don't seem to be able to observe the program "dynamically" so to speak. One consequence of that is that I don't know whether or not the program has reached the breakpoint.

Is it possible to observe the running program online, or do I have to set (extra) Merker at different places in the program and then observe these in a VAT?

I set up the conditions that should have caused the program to run up to the breakpoint, but in the VAT some Merker which I would have expected to be set weren't. That could, of course, have something to do with the fault I'm chasing - or there again, maybe not, since I don't know whether the program hit the breakpoint or not.

A thought just occurred to me, if the program hits the breakpoint effectively it has stopped running. Do the CPU LEDs go to STOP in this case?

TIA

Roy

PS Another thing I noticed, was that all the Blocks from the main program are still visible online, although I loaded a very cut-down version of the program. It's a slightly worrying thought that under some fault conditions you might suddenly start executing code that you didn't even think existed. Is this a real possibility? I think I might take to deleting the MMC in future, just to be on the safe side!

Answered my own question this time.

When the Breakpoint is set it is indicated by a red ring at the left of the line of code.

When it's activated, the ring is also filled red.

When the program hits the breakpoint, the CPU goes into STOP and an arrow points to the breakpoint which caused the halt.

The only thing now that's a bit of a pain is that when a breakpoint is set you don't appear to be able to view any other parts of the program to see what's happening there - or is there a way round this problem?

Getting the Breakpoints working is one thing, doing something useful with them seems to be something else again!

I've set up a VAT with all the relevant Merkers etc. which are being used in the program, but ones that MUST have been set in order to hit the Breakpoint are still showing up in the VAT as FALSE. If I try to update the VAT with F5 while sitting at the Breakpoint (CPU in STOP) then the VAT gets wiped clean.

Does this mean that the only bit of information you can trust is the Status Word panel which pops up when you activate the Breakpoint. If so, it's a blooming uncomfortable way to have to faultfind!

Or am I missing some simple away to aquire more information after the program's hit the Breakpoint?

This is slowly starting to get frustrating, especially as I've now got a deadline to work to - 7th Feb. Sounds like it's a long way away, but if things continue the way theyve been going for the last day or two, time is going to fly by much too quickly for comfort!

Mmm, maybe I was expecting too much from the name. If you don't regard it as something resembling a breakpoint in a PDP11 or VAX program (for all I know PC Programs as well) where you have a stack of information available and instead regard it as a sort of superior Single-Step system, then you get there in the end.

It's not that fast, but now I've at least found my first Problem, so things are at least moving in the right direction.

Great that you share your experiences here. I could use this someday

If I try to update the VAT with F5 while sitting at the Breakpoint (CPU in STOP) then the VAT gets wiped clean.

Click to expand...

I am speculating that the VATs only get updated at the end of the program scan, and as the scan has been interrupted by the breakpoint then it could explain it.

The only thing now that's a bit of a pain is that when a breakpoint is set you don't appear to be able to view any other parts of the program to see what's happening there

Click to expand...

I think this is because the online view of the code is only updated when the particular code is scanned. This is the way Siemens has decided to make online viewing of program code - it is syncronous with the program scan - whereas other manufacturers online view is not syncronised with the program scan. Both ways have their advantages and disadvantages.

I think that it should be possible to view the online status of DBs, even with a breakpoint set (not sure though - you may have to try it). Of course, it will be a pain to have to jump about in several DBs to view different addresses.

Great that you share your experiences here. I could use this someday

Click to expand...

Thanks, but I think that's what the forum is all about.

The way I see it, as far as possible all the information about a problem should be kept in one thread, so that somebody else searching for information should find everything he needs in the same place.

I am speculating that the VATs only get updated at the end of the program scan, and as the scan has been interrupted by the breakpoint then it could explain it.

Click to expand...

Just to complete the picture, courtesy of RolfB at SPS-Foren.de, to update the values in the VAT while stopped at the Breakpoint, you use F7 not F5.

That's what happens when you are so used to using F5 for refresh, that you don't bother to open up the Variable menu in the VAT!