Hello experts,

Imagine S7-1200 PLC talking with HMI KTP700 basic over PN hmi connection.

On HMI screen is only circle, in animation appearance is plc input I0.0.

When plc input is 1 circle turns into green while in 0 turns into red color.

Hmi takes symbolic access to the I0.0 value of the PLC.

PLC hw DI filtering to 6.4milisec.

When I0.0 is 0 then circles color is red without any issues.

When I0.0 is 1 then circle is constantly flickering from 1 to 0 with period of selected acquistion cycle in hmi tag settings lets say 1s. Changing the acquistion cycle to 100ms makes the flickering more frequent.

The question is not how to get rid of this issue. This can be easily done by making FC to gather inputs and save its value into M or DB area and then reading those retyped tags in hmi.

The question is what kind of settings in plc or hmi (hw/sw) should I pay attention to to get rid of this stange behavior.

The most valuable thing from this would be for me to understand why its happening or how its possible to even happen.

I am doing plcs for like 10 years, siemens 6years, 4 years rockwell/beckhoff but it looks like its never ending learning with siemens.

PS: with tia version lower than 16 have no issues with reading direct PLC DIs into HMI so I dont know its tia16 issue or hw/sw settings issue I made. Tomorrow I will try to delete IM folder and recompile but I dont know.

Thank you for your suggestions in advance.

Dear experts, thank you for suggestions.
Here is a video youtube-TIA16-behavior.

After brainstorming the plc project, I opened program info > device assignment list and I found, the total basic elementary issue.

There was declared IW0 as int and found many other PIWs used in plc sw.

The IW0 was used as a return value of RD_SYS_T (read system time) and of course IB0 IB1 was used for standard DIs in HW cfg.

PLC program looked like copy/paste from diff project so I had to edit a lot of things.

After everything its working as expected even in TIA16.

So I think I found WHY its happening, but did not even expect the fault like this.
It reminds me while debuggung on 10 station pallet line simmilar strange behavior.

The problem there was always false bit used as IN/OUT of FC doing program stepper.
And of course, the FC writes the value TRUE into PLC managed always false M area bit.

I hope I dont dissapoint you, but it happends while company programmer dont know what is doing.

We will never ask that company for any contract.

Once again experts,

Thank you for your time!