Dear all,

I am a newbie to the world of siemens plc, so pleasehavepations with me understanding all you suggestions / questions

We currently have a CPU (CPU315 2 PN/DP) with a serial communication card (CP340) that communicates with a Laser (LPXpro 240), communication is ASCII, 9600, 8 bit,

The problem is that random the CP340 will lose communication with the Laser, and in doing so it will not generate any alarms and freezes!

(we have this happaning on all systems, 3 in totall)

Findings:

1) TXD & RXD stopt flasing and are both OFF

2) SF is OFF

3) On the CPU no alarm red lights

4) Profibus profinet ethernet are all working

5) AI AO DI DO are all working

6) Resetting the laser will not clear the problem

7) Dis-connecting and connecting the serial cable will not clear the problem

8) Doing a MRES on the CPU will not clear the problem

The only thing that clears the problem is to disconnect the 24VDC to the CPU and connect it again ?

I have bean reading and found one treat that looks like the same issue and I checked the advice that was in there.

"I dealt with my problem. It was, as always, my mistake. I did not know that there is a fixed number of frames in the buffer of the CP. I set "Buffered Receive Message Frames" to 1 and unchecked "Prevent overwriting" in the HW Config of the CP under "Parameter.." >> "Protocol">>"Receiving Data" and everything worked fine. "

I looked at the settings and they were already set like this

What I like to do is to see if there is a error massage that I can check, but I dont know were to look.

I did found some info thatmight help!

DB13.DBX 188.0 receive_succes = ON

DB13.DBX 184.3 receive_timeout = ON

Somine question is:

1) where to look for the error messages of the CP340

2) suggetions on how to trouble shoot a issuewith RS232 communication

Help is much appriciated

With Kind regards

André

Dear André_1976,

for it seems that you have a problem on your serial line (incorrect frame data) and or an unstable program handling the communication protocol with the laser.

In both cases you will not get any visual intication on the CP or CPU. You can compare it with a wrong logic in your S7 software. If you program an AND instead of an OR in your software you will not receive any information about it, even your program does not work properly. This is the same case.

Try to check with the developer/vendor of your software.

Best Regards.

@eisenpferdreiter

Thanks for the information, I have bean reading it, and know now how to check the Buffer dignostics of the CPU and the CP340.

Hopefully I can see a message next time it locks up.

@ TIBI68

Not sure what you mean by an unstable program, it could be running for 1-2 months without any problems, and all functions and feedback is working fine, and just out of th blue it will lock up.

Contacting the developer (mine colleuge, aStep7 software engineer) I already did, but he says he cant find it and he did it as the manuals told him to do it, and in his eyes its working. So thats why I am trying to solve it, because he is not taking any steps to solve it

Thanks for allthe input, its much appriciated

Kind regards

André

Dear André_1976,

you have a very nice and helpful colleague

I beleivethat there is a conditionthe softwareis nothandling properlyand let the driver crash (stop working). A trace would be very helpful in that case.Unfortunate it's not so easy to take a trace on a RS232 line while both devices are connected, only with special equipment.

Maybe you can program a timout and reinitialize the communication when it times out.

I just had a quick look into the manual of the laser.

The PLC is the active part in the communincation and the laser replies to the commands and setpoints coming from the PLC.

If the Tx LED on the CP stops flashing you need to check why the PLCdoes not continue sending its telegrams.

Most propably thePLC it is waiting for something.

And waits.............

Leave it to your colleague to fix this part.

Best Regards.

Dear TIB68,

Thanks for taking the time and efford to check the manual.

I will propose your suggestions, and as soon it happends again I will see if I can get some info out of its buffer diagnostic.

I am also in the works to get some kind of spy cable, maybe we can find it that way!

Dear Zahra Hatampour,

Thanks for you suggestion, these settings are checked and are correct

Kind regards

André