When both our system communicate it is not working - A0FF error is coming

Thanks a lot Mr. Duris,

I have been able to simulate all signals via Modsim to my PLC and as of now it working fine. There was a Write_Read bit which I had to set to true to be able to write to coils and it worked.

But I have another issue now, I am able simulate with modsim successfully. I am also able to recieve data via Modscan from GE successfully. But when both our system communicate it is not working. I mean there is communication coming and going.

I try to check i found my CP is terminating the connection. i see in the status the A0FF error is coming and clearing more or less like a pulse. 

I found someone having the same issue in the below link,i tried to make the UNIT as 1 still the same problem exists,

https://support.industry.siemens.com/tf/ww/en/posts/s7-400-to-pac3200-modbus-tcp-issue/142200/?page=0&pageSize=10

Please advice

Mr. Duris, I have attached the configuration in the attachment. Please kindly help

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Split from 443-1EX30-0XE0 - Client is not working.

Yes Mr. Duris

I know the difference between the connection ID and UNIT ID. Yes sir, I understand that UNIT is related to slave address. I tried to change it to 1 only to try if the solution works. 

I think maybe it is related to other parameter. I guess

Mr duris,

i am acting as a client (single 400H CPU) with one CP (MODBUS TCP IP CP 443-1). I am connected from CP to the optic fibre convertor and on the other side. GE recieved the data data as a slave from the other end using the optic fibre convertor with TCP IP as well. 

The problem I am facing is that both are not able to communicate with each other. And i recieve this error in the status of the calling block modbus param A0FF. This error is coming and going. I try to read the diagnostic from CP it says the Connections was terminated by the CP. 

By simulator it is working on both sides but not in actual. I even checked the opric fiber convertor it is working fine. 

Basically the communication between GE PLC and my PLC is not working

But i still dont know why they are not able to communicate. 

Dear Mr. Duris

I really appreciate Sir, thanks. Please help

1. Yes 

2.Yes

3. Yes it is number 3. I tried to test the functionality of both sides using simulator  and it is working.

now the cummunucation is working but still some issue. Somewhat close to solving it  

actually you are right it is related to the length of the modbus param db  but the thing is I am not using any more than 125 registers  if you see my FC901 in the attchment  i was triggering every one second the length for each data type. But still it was not working.

now the cummunucation is working. I found the problem but still need help. It is related to length used in the DB parameter of modbus. When I removed the length parameter from the OB 1 calling, it was 21 then because at the time of triggering it got loaded into the DB param  

I even tried to change the triggering time still no help

If you see the block FC 901 in the pdf. In this block i am triggering the length for each type of data. My exact question is what exactly the value of length i should be using for the communication to happen. Do i have trigger for each data type or not. If not then what exacrly should i use. Because say for instance i used 5F (95 in decimal) only imput status is only working not input register. So basically on what grounds i have to select it if i dont use triggering.

if i am using triggering for ea h data type for the length why is it not communicating. Or do i have to keep it constant for all data types. Really it is not clear to me. 

If i use this triggering then the communication does not happen with GE. So what Length should i decide. I am really confused with this

Even this Length I try to make 0 or FFFF still no success. 

I try to play with the Length but I am still not able to recieve the entire data.

If i used length 30 I recieve the entire Input register and some Input status

If I use length 100 I recieve Entire Input Status but not Input register. I am really fed up of trying. I am in the site and no results. 

I really dont understand how to adjust this length ot to do what with it

I did one things as a last trial.

I made the lenth of each data type.That is I made number of signals in the

1) inpur register as 100 

2) Input status as 100

3) Coils as 100

 ofcourse including the 2 bytes for reserved data. But still no luck. Already the spares are there, so its already taken care of. It works in the simulator but is not able to communicate to GE PLC. 

Then there was a suggestion of using each data type per each call of the FB MODBUS. It means one call for only coils , one call for only input register and one call for only input status. But for me that does not makes sense, if this is how it will work then why the example includes different type in one call.

That being said, I still am wondering what exactly should I have to do to solve this issue. Really getting out of my league.