Hi everybody.

I have trying to implement a modbus communication between an CPU S7-1200 and an Sentron PAC 3200, but without success. I am using an CPU 6ES7215-1HG40-0XB0 (TIA V13 only)., with an CB 1241 RS485 (6ES7241-1CH30-1XB0) and a PAC 3200 with PAC RS485 Module (7KM9300-0AM00-0AA0).

I am using the CPU like a Modbus master. In the main program I used a MB_COMM_LOAD_DB and MB_MASTER_DB. After program download  the CPU start comunication but dont get any data. My main doubt are:

1 - If I need to read the offset 1 - Va-n, I should to put it in Data_ADDR, ok? But, how I should to refer address: like 1 or 40001?

2 - In Manual-Modbus-RS485_PAC3200 there are the complete list of offset registers. Other point is: using the same exemplo: the offset 1 (Va-n) is a float (I could to use a Real type in the program?).And finaly, if the offset 1 have 2 registers (each register have 2 Bytes I suppose?) so the data_address is 1 and data_length is ??? 1, 2, 4 , 8, 16, or 32 .... I dont have any idea.

 
If Somebody have an simple exemplo of application will be very apreciated.

I don't know Modbus and Sentron PAC, but I found this:

https://support.industry.siemens.com/cs/ww/en/view/40614428

Are you shure your Sentron PAC talks Modbus RTU and not Modbus TCP?

Hello,

After several attempts and a lot of reading manuals, I managed to solve. Here's what I did:

The problem was in the offset. In the documentation that I had read, always talked about offset 40000 (or 4x) then what I was doing was: I used the address of the device data (eg address 1) and sum it to 40000 in the configuration of MB_MASTER block thus the starting address that I was setting was the 40001. But after a little more research, I realized that the CPU 1200 documentation says that the function 3 (function I was using for reading Registers holding) can be used to read addresses between 40001 and 49999. It turns out that one of the devices (one Weg softstart) owned a parameter with address 0 ... when I saw it, it occurred to me that I should actually add 40001 and not 40000 as I was trying to .... made this change, the program worked perfectly. I had tried to read other addresses, and some seemed to be read, but with inconsistent data ... then I realized the mistake I came to understand why the inconsistency ... is that as I added up the value 40000 to the parameter address .. . I was actually indicating that the initial data address should be read from the least significant byte of the DWORD (ie, starting the third and fourth bytes) ... and that caused the error or inconsistent reading.

Conclusion: When using a S7-1200 CPU, simply add the address we want to read the value 40001, so for example:

If you want to read 5 records of the type INT (2 Bytes) starting address 101 (ie 101,102,103,104,105), just configure MB_MASTER with data_adress = 40102, and data_len = 5, and point it to a struct of the type INT data, with 5 elements.

If  you want to read 4 records of the FLOAT type, from the address 61 (ie 61, 63, 65, 67) *** Note that in this case the record occupy 4 bytes and not 2, so the addresses are 2 on 2) then you must configure the MB_MASTER with data_adress = 40062, and data_len = 4, and point it to a struct of the REAL data type, with 4 elements (Case PAC3200).

Important information: In case where there are gaps addresses, e.g., 101, 102, 103, GAP, 105, 106, 107 ... yet the device of the adresses are listed continuously, as exemplified, it is not possible to reading in a single request, ie in this case is not set up a DataLen = 6 and start reading the address 101 ... an error occur because there is no address 104. Already can not do the data_len = 7, imagining that the GAP will read zero, eg ...

In such a case, one must make two requests, one for reading of 101-103, and a second to read the data 105-107.

Hi Rui_Nobrega

  Could you please send the program (pdf or picture) you wrote to establish a communication between S71200 and PAC 3200?

Sincerely,

Hello,

simply look at this conference for topics depended to Modbus RTU. There you can see examples of users and can imagine better what's going on.

Thank you bro !!

I used it register in labview, but I used it to read and I started from  register 1 as the manual register modbus say it, but Im gonna try with the 40001 register  to read values