hi

I have 1200 PLC 6ES72121BE400XB0 with RS485 Modbus RTU card 6ES72411CH320XB0.

I am very confused which modbus blocks shall i use from the library to get it running as Modbus Master:

• MB comm load version 3.0
• MB master version 2.3

OR

• MB comm load version 2.1
• MB master version 2.2

Could you please advise me ?Is it not strange that mb load block is on different version than mb master block?

Many thanks in advance

Hello,

don't be confused, use simply versions which are presented to you in that time (don't click on versions), this works ok in most sitautions. If something not works, you can try other versions. Look to that selection, you have available for first main version of instructions as type (RTU/TCP), then each instructions with more versions. All is available also due your selected CPU version and firmware.

Hi 

Thank you for your reply but could you please guide me a little further?.

There is selection between:

 Modbud RTU family (latest versions are 3 for load block and 2.3 for master)

and Modbus family (versions 2.1 for load block and 2.2. for master)

My PLC is connected to gateway-00 to translate modbus rtu to modbus ascii but in the office i don't have access to the particle counter which is modbus slave and cannot test communication properly.

When i selected modbus RTU block i was getting 8281 error which suggested problem with port configuration but when using Modbus family blocks i get no status error (except slave timeout after some time) but once modbus master block is triggered it is constantly busy without ever finishing. I was trying to simulate modbus slave replies (feeding back messages from my PC using putty program) but it did not help - the block is busy all the time.

So at least i would like to be sure i am using correct blocks - are you able to advise if i should use Modbus family? Any suggestion about master block being busy all the time?

thank you for great support on the forum

Regards

Hello,

I'll be for first check proper gateway functionality. Can you confirm this? You can check functionality with 2 MB applications on each side of gateway. Your situation can be little bit problematic because of 2 different MB protocols - MB RTU and MB ASCII. On one side you need MB RTU application and on other MB ASCII application. Sry I don't know your Modbus experience, therefore hard to recommend something. With correctly working gateway you can jump to other tests, without this exactly to know, other tests are waste of time.

MB -> Modbus...

i fully agree with your suggestion i am just downloading modbus simulators.

thank you

Hi, it's a bit like the weather. As it happens I just tested the latest mb-rtu at v14sp1 1214 v4.2 and it didn't work. mb_comm_load gave a 81AA error, not documented. I retried with the 'old' version and it did work. Yes very very confusing. I had the same with the tcp versions.

The only advise I can give is make sure your side of the modbus is working and then trial and error the Siemens side with different versions. It's a moving target (modbus being brand new innovation;)

The "latest' version enable the use of rio cm's so if you don't need that you fine usign the 'old' blocks'

Hello,

but pls explain what is your situation, did you check something about gateway? What device you have connected to PLC now? Pls share photos of program blocks in Online also. What Siemens SW you're using now, only for sure?

Hi, as said, you could try with the 'old' instructions v2.1/2.2. In that case the mb_master/slave db doesn't have the MB_DB struct inside so you pass the whole DB as a para for mb_comm_load.

As you see It could help if you specify exactly which versions plc + tiayou are using.

Just to give you the heads up I retested with the 'new' block and also got an 8280 error (I'm using the slave instr). V2 instr. are working a cb1241 (also cm232/485).

And that's with tia14sp1upd1 1214 v4 fw 4.2.1 at 16:45 this day, this place, without drink;)

Sorry, it's not me making it difficult.

Hello guys,

in my opinion without clear info about correct functionality of Gateway, all other steps are waste of time. The situation is not clear to me now, hard to recommend something. Also inclusing infos about TIAv14 with same, don't have TIAv14 and don't know if user have step up to this version now.