Siemens S7-300 CPU318-2 Newbie Questions

Hi - I am unfamiliar with Siemens PLCs but have been given ownership of an S7-300 CPU318-2 with IO and a network interface card at site. The PLC is working fine but there is no documentation or disks. I have the following questions:


1) Can I download the user program for safe keeping?
2) If answer 1 is yes what software and programming lead do I need to purchase?


Cheers!

For a 318-2 you would need Siemens STEP7 v5.6.
If the network card is a CP343-1, then you can go online with Ethernet.
If not, you would need for example the PC Adapter USB to connect to the CPU.

Note that the CPU is possibly password protected. In that case dont count on being able to go online with the PLC at all.
Someone may claim that you can bypass the password on an S7-300 if you know how, but I wont provide any details on that on this forum. It can hurt Phil if someone tries !
The password bypass for an S7-300 also wont work with a 318, since it is actually an S7-400 in S7-300 clothing.

Also note that some may claim that Siemens TIA Portal is also compatible with S7-300 PLCs. But there are serious limitations, and you cannot assume that you can go online with and support an old S7-300 like the 318-2.

JesperMP said:

Note that the CPU is possibly password protected. In that case dont count on being able to go online with the PLC at all

Click to expand...

Hi Jesper - Thanks for the quick reply!

That was my worry - do I invest in the kit only to face a password??!!!

I do know that the Web Interface for the PLC displays some standard info but asks for a password when you click on more detail - Would that mean the user program is also password protected?

Also there is a memory card on the CPU would this make any difference?

A 318-2 does not have a webpage since it does not have an integrated ethernet port.
Maybe you have in reality a 319-3PN/DP ? Its type no is 6ES7318-3EL01-0AB0 which may confuse.
Exactly what is the type no of the PLC ?

The webserver and the CPU passwords are not the same.

You cannot read out the memory card.

JesperMP said:

A 318-2 does not have a webpage since it does not have an integrated ethernet port.
Maybe you have in reality a 319-3PN/DP ? Its type no is 6ES7318-3EL01-0AB0 which may confuse.
Exactly what is the type no of the PLC ?

Click to expand...

The PLC CPU is part number 318-2AJ00-0AB0

Does the ethernet card have a webpage?

The ethernet card is 343-1GX11-0XE0

My plan of attack is to download the trial Step7 5.6 software and try to connect to the CPU via the ethernet card before I spend any money

Yes the ethernet card can have a webpage.
The trial of STEP7 v5.6 could be the best way to test if you can access the PLC.

Is it a second hand machine or just a PLC for testing / learning with?

If it's the latter, not worth the effort, it's old HW and old SW, you can get 2nd hand S7-1200 for £50+ on eBay to play with (unless of course you really NEED to learn the old Step 7 stuff)

If it's a 2nd hand machine, as you say just download Step7 trial and try and upload.

Ok - The good news is the PLC didn't have a password so I was able to successfully use the trial software to upload the blocks and hardware from the PLC onto my PC for safe keeping

That is good from a backup/get out of jail point of view but I have another issue:

The SCADA system which talks to this PLC recently had its Kepware OPC component updated and since then some of the data within the PLC has failed to be read across to the SCADA database

Kepware have offered the following solution:

The "Symbolic Access only" block attribute restricts access to the data block from external connections. This setting is checked by default in the controller ladder software. To prevent this error, uncheck the "Symbolic Access only" block attribute. Then, re-load the ladder project to the controller.

It worked fine before this 'upgrade' so I'm not too sure if the above solution is valid

Does anyone know if I can implement the solution to see if it works and provide a few pointers on how to do it - As I said previously I have not had any experience of Simatic PLCs/software until now

I dont think there is such a "symbolic only" block attribute for the data blocks in the 318 controller. You can always access the blocks by absolute addressing.

Maybe this 'solution' refers to that in the newer S7-1500 PLC blocks that are compiled as "optimized" can only be accesssed by their symbolic address. That does not apply to the S7-300/400 generation CPU that your 318 belongs to.

It also is weird with the instruction to 're-load the ladder project'. What do they mean ? If by ladder they mean code, why should that affect the ability to access data ?

I would ask Kepware, excatly where this setting can be found.
If nothing has changed in the 318 CPU, what is it that the Kepware cannot do now that it could before the update ?

Hi Jasper

Your reply makes sense to me after looking at the code blocks.

We are going to go back to Kepware to try and get this sorted as everything was fine before their 'upgrade' was implemented.

Although the PLC is old it is still more than capable (in my view) of performing its duties monitoring and controlling (a small electrical substation)

I've worked on PLC systems much older and provided they are left alone they are normally very reliable

Thanks for all your help in getting this PLC backed up

Maybe worth showing a screen shot of the errors reported by Kepware, this may give someone here an indication of the problem. I agree with Jesper, It does not make sense for a 300 controller.

What kepware OPC quick client shows for tags. Are they all good for same tags which are errors on scada.
It helps to know if errors are on kepware addressing for 300 or OPC symbols <> scada side.
318 addressing is S7 protocol with DB addressing for kepware.

Question:
Are the missing tags of a certain data type? Such as only Reals are not working, or only bits are not working?

Not saying it's true in your case, but I have encountered new "OPC drivers" that used slightly different syntax upon upgrade from DA to UA, do you know what the upgrade was exactly?

That suggests to me that during the upgrade certain types of tags have changed or the upgrade requires some other format, my suggestion is to check the tags for type etc. it could be anything from the tag description to the data type, Are the tags visible in the kepserver configuration (it is not actually required to configure the tags only the paths or devices I know in IFIX it is possible to configure the tags in a way that kepserver does not have a copy of the tags). If the tags are visible in kepserver configuration try creating another one, for example if you have an existing tag called My_DB_Tag_1 create a new tag with a different name, configure it by following the help on the Siemens I/O driver help, see if this works. If so you may have to re-configure all the tags that do not work. From your description if you can read all tags in the client supplied with Kepware but not in the Scada it is not a problem in the PLC.

The tags involved are a certain data type (actually metering totaliser data) the bit signals from the switchgear status etc. are all working normally. Unfortunately the technical discussion is going on between the SCADA vendor and Kepware so I am somewhat out of the loop on a detailed technical level. Also because the system is behind a firewall I can't see the Kepware software on the SCADA server and only have access to a normal SCADA client. I do know they managed to get some of the signals restored but seemed to be unable to get them all back (Maybe some sort of limit I the number of signals being read?) I'll try and get as much technical detail from them and report back when I know some more.




In the meantime many thanks for all the suggestions of things to look at - I'll try to pass these on to the people involved.