ModBus RTU - Modbus_Comm_Load Issue

Hello,

I'm currently having a hard time establishing a connection/retrieving any register data from my slave device. I think issue might be in the initial Configuration/Modbus_Comm_Load portion. I've read through the "How do you establish a MODBUS CONNECTIONS" article, so I have done some initial reading and research on the topic.  

( https://support.industry.siemens.com/cs/document/47756141/how-do-you-establish-a-modbus-rtu-communication-with-step-7-(tia-portal)-for-the-simatic-s7-1200?dti=0&lc=en-WW )

Question: Based on the above article, we are suppose type in the instance data block of the master or slave block (master in my case) in the MB_DB parameter of the Modbus_Comm_Load block. Yet, when I do this the address gets highlighted in RED and I get a " the data type Modbus_Master of the actual parameter does not match the data type P2P_BASE_MB of the formal parameter".

Any insight on what I'm doing wrong??? I'm sure I might have overlooked something.

Thanks, in advance

SCR 8893

Found the issue ... for whatever reason tia portal v13 has two Modbus folders ... one named "Modbus (RTU)" the other "Modbus". Both folders have similar function blocks, however when I use the function blocks from the "Modbus" folder and place the instance datablock of my MB_MASTER in the MB_DB input of the MB_COMM_LOAD function block I do not get an error.

Does anyone know why this is ? Thanks, in advance.

Sergio

The S7-1200 system manual explains the difference in section 13.5.3.1:

● Modbus RTU instructions (Page 958): These Modbus RTU instructions provide all of the functionality of the legacy instructions, plus the ability to connect to PROFINET and PROFIBUS distributed I/O. The point-to-point instructions allow you to configure the communications between

FYI, the legacy instructions are MB_COMM_LOAD; MB_MASTER; MB_SLAVE. The 'new' versions are Modbus_Comm_Load; Modbus_Master; Modbus_Slave.

Did you find what is problem? Now i have that problem

Efrem95

Did you find what is problem? Now i have that problem

Welcome!

We require some minimum information about your application and the hardware used. We ask this so that we are certain to have all we need to address your submission correctly. Also be so kind to post your question only once. This allows the forum volunteers to focus their time and efforts efficiently on more topics.

Thanks for understanding and meeting us half way.

I found that info in manual.

True, the histrory has no records where lies th legacy and where lies the fresh.

Although... if judging on the block's images provided in manual the legacy has a tiny extension triangle and the fresh is without one. Also similar blocks have different names.

BR