Siemens DBB VS. DIB any difference

[JOLTRON]

Sorry if this is a basic question, but this is the first time I have run across this.

I have a program written in STL, and it has a:
T DIB 8

I did a search in the Siemens help section and it only states that it is a keyword for a data block, just like DBB.

Is there any functional difference between the two? The help file is very vague in this area.

From what I can tell is that DBB works in the last opened DB, and it looks lik DIB works in the STAT area of the current FB, similar to how an LB would work in the TEMP area.

Am I close?

 

[L D[AR2P#0.0]]

DBB accesses the current global DB
DIB accesses the current instance DB - if the access is inside an FB then this will access what ever variable is located at DIB8 of the instance DB. An example of a disaster waiting to happen should someone change the interface of the FB.

 

[PeterW]

DBB is the opened datablock and DIB is the opened instance DB.

If you are in a FB then it is the IDB for that FB, you can open a IDB at any time (Or even a normal DB as a IDB)

It is useful if you are passing data (non sequential) between datablocks and you don't want to keep opening DB's.

i.e

OPN DB10
L DBW1
OPN DB11
T DBW3

OPN DB10
L DBW6
OPN DB11
T DBW15


could be

OPN DB10
OPN DI11

L DBW1
T DIW3
L DBW6
T DIW15

 

[JOLTRON]

Thats what i was thinking. I'm not a fan of using the absolute address like that, especially when we have some newer people not very familiar with siemens. I remember when i made the rookie mistake of inserting something into a db when the processor was set for absolute addressing. Took me a couple of hours to figure out what i did.

I know it can make for standard/reusable code, but it makes it difficult for new people to trouble shot. Just like using the STAT area of a FB inside the FB with a local call and then using the full name in another block to access it. That wouldnt be a big deal if it would show up in the cross reference or the goto location.

Forgive any typos, entered from my phone.