Greetings.

I am trying to update the way a communication in PCS 7 is made. We use redundant CP 443-1 through Modbus/TCP. Both the S7 and the devices are redundant.

I downloaded the corresponding Modbus Blocks library, the additional Blocks for communication and the TCP Wizard:

Block library for redundant Modbus/TCP communication via CP443-1 or CP343-1 - ID: 109760021 - Industry Support Siemens

Add-on blocks for Modbus/TCP communication - ID: 62830463 - Industry Support Siemens

Simatic S7-300/S7-400: Wizard for creating connection data for Modbus/TCP communic... - ID: 60735352 - Industry Support Siemens

I've been going through many manuals, but the one I have been using the most can be found in the following link

Modbus/TCP - Standardized and redundant Communication of PCS 7 with Third-Party Sy... - ID: 75867147 - Industry Support Siemens

First, I don't understand the difference between what is called in the manual a Job and a Telegram. In the manual, job is used for configuration done in the "Job_List" and Telegram is used for the block "MB_REDCL". The picture attached shows an example of this, found in page 52 of the manual I mentioned.

Because of the way the communication works now, I am trying to use DBs for sending data, and CFC data collector to receive data. I think I understood how that works: with the DBs, I will need one DB for each job, in which I will reference inside the "MB_HPARAM" DB. For the Data Collector, the data will be written inside the instance DB of each block that I add (in this case, it will be MB_OUT_W).

1. If that is correct, my main question would be: why do I have to use the Job_List to make different jobs? Doesn't the block MB_REDCL already do that? It already has the config of all the jobs in the "MB_HPARAM" DB. The only explanation I can think about is that the Job_List allows you to flip between reading and writing in the same MB_REDCL block. Is that it?
2. The secondary questions would be: If i use the Job_List Block, do I have to also configure the parameters for "data_type_x", "start_x" and "end_x" in the "MB_HPARAM" DB?
3. And lastly: Is it possible to make more jobs than 8 using Job_List? I know I can expand the block, and I have done so, I just don't know if that would work because I didn't understand if we need to have matching configuration between "Job_List" and "MB_HPARAM".

Any help is appreciated.

PS: I have gone through the example project, but the ones that use CFC are extremely simple and vague. They don't show examples using Job_List and I couldn't find any example project for the usage of Job_List or the additional blocks.

Thank you for the explanation, Wüstenräuber.

If I understood correctly, the block MB_REDCL does the "link" between the telegram that it is executing and where to write the data by knowing which register is being read/written. If that is the case, do you know if it would be possible to just add more rows to MB_HParam, for example: "data_type_9", "db_9", "start_9" and "end_9", "data_type_10", and so on? Because from what I understood, we need those informations in the PARAM DB to be able to read and write stuff from the registers to a DB.

Another thing that I noticed is that in the parameters for the telegram, it is used the length of the registers, whereas in the MB_HParam, the end addresses are used, but that just means we have to add the same information in a different way in the two blocks.

Thank you again, Wüstenräuber.

The reason I wanted to separate the communication in different Telegrams is because of the way the communication works now. They have many gaps in between registers that are read/written and some that are not accessed, but I understand the concept you explained and I will be using something similar.

Thank you very much.