Siemens S7-1200 / S7-1500 and Modbus TCP MB_SERVER

[yell]

Hi, I'm facing a problem with Modbus TCP communication using an S7 1500 as Slave (Server).

I configured the MB_SERVER function block and I'm using QModMaster as Master (Client) to test the system.

The communication is working and I tested the following configurations:
a. with an array DB of Words (or Bools, or Reals) I'm able to read them with FC3 on (4)0000+ addresses. See 1st MB_SERVER on pic1.
b. if I use a pointer, e.g. P#M100.0 BYTE 18, I'm able to read the inputs from %I0.0 onwards and I can read Discrete Inputs (FC2) and Inputs Registers (FC3). See 2nd MB_SERVER on pic1 and pic2.



My questions:
1. Why the pointer reads the inputs from %I0.0
2. How to configure the server to read from a mixed DB. I tried to use pointers to read the data inside a DB but with no luck. I would like to read data as pic2 but without allocating inputs images (or at least not starting from 0).

Advices?
Thanks

 

[boneless]

Not sure I understand your question, but I would move all your data to one single DB. You can do multiple calls with smaller area's, but this is so much easier.

I am doing a similar thing this week. The client is reading and writing directly to all of the registers.

 

[yell]

Thanks boneless,
I already tried that configuration, that is the simplest and most obvious.
But that configuration has a downside: booleans can't be read with Modbus FC02 because are put in the holding registers and translated in words by the FB. You can read the booleans with FC03 and the bits are swapped (see the screenshot here attached).
It works, but I don't like it.

Maybe is a problem of Modbus Master software?
I don't think so because I can read the bits correctly with the configuration in the 1st post.
Let me know if you have or not my same problem.
Maybe I am totally crazy

 

[boneless]

The master (not my scope) reads all the data with the same function code (I think). He then extracts the BOOLEANS from the registers.

We did have to do some swapping (he uses Schneider), but works without problems now.

 

[yell]

Ok, thanks. Seems the simple way.

Btw, I think that I understood how this block works.
It maps the Siemens discrete IO with FC01 and FC02, without additional configuration.
Cool. Finally I found out how it works.