ST and HF ET200S modules with PCS7

Hi.

I have doubt regarding the use of ST and HF modules in ET200S with PCS7.

I have three applications using ET200S with PCS7 in different ways:

1) IM151-1 HF
     DI modules HF
     DO modules ST
     AI modules HF
     AO modules HF
(In this case it operates without system error messages)

2) IM151-1 HF
     DI modules ST
     DO modules ST
     AI modules HF
     AO modules HF
(In this case it operates without system error messages)

3) IM151-1 ST
     DI modules ST
     DO modules ST
     AI modules ST
     AO modules ST
(In this case but it operates with system error messages. I think the messages error are because IM151-1 ST is not released for PCS7)

My question is what is the correct way to use and the differences in using the ST and HF modules with PCS7 ?

Best regards.