In the very first time of running our S7-300 we have error as follows,
---------------------------------------------------
Area length error when writing (and also reading)
Global DB, double-word access, Access adress: 78
Requested OB: Programming error OB (OB121)
Priority class: 12
Internal error, Incoming event
---------------------------------------------------

does anyone have an idea for this problem?

Pavel_II

I am beginner in simatic. I had very similar error diagnostic. CPU was stopped, even with OB121
Analog input was set wrong : %IW142
Then i set: %IW142:P (peripheral)

after this, fault disappear, and CPU go RUN.

Hello,

yes, but better will be look at CPU diagnostic buffer where you can see all events and related error notification. Look at first post where is this listing showed.

I get the same thing also, how do you know the actual attempted DB being addressed?

What indicates a block / network of the offending instruction?

I got the following from my diagnostic buffer, OB121 is loaded in the processor so it does not go into stop.

Hi rtuncer,

This error is due to either DB is not loaded or DB is of shorter length. So initially download all DBs.

Select statio n and press control D. Now go to dia. buffer tab. Select the diagnostic entry and press Open block. It will open the block which is responsible for causing error.

Sachinpatke

Hi rtuncer,

This error is due to either DB is not loaded or DB is of shorter length. So initially download all DBs.

Select statio n and press control D. Now go to dia. buffer tab. Select the diagnostic entry and press Open block. It will open the block which is responsible for causing error.

 JUst before this switch to online and delete OB121