Hi hirorama,

The problem is therefore caused by the interface module.

You are using the SIMATIC ET 200SP, PROFINET interface module IM 155-6PN Basic, which has a very limited range of functions. In your case, the maximum address space of 32 bytes is the limiting factor.

Since each SIMATIC ET 200SP analogue input module AI 8xI 2-/4-wire BA occupies 16 bytes of address space, you are limited to 2 such modules.

Assuming that the analogue inputs are required, the cheapest modification would be to replace the interface module. The SIMATIC ET 200SP, PROFINET interface module IM 155-6 PN ST provides 1440 bytes of address space. This is more than you need.

Kind regards
Stefan