Hello,

Please provide assistance with understanding the STL code below: 

• What does "BLD 3 = L 6.0" and "BLD 4" do?

It's BLD 3 alone and in general, it means nothing (same as BLD 4), as it's not an instruction for a CPU.

And, separately  = L 6.0, which is added by a compiler and probably is used to store the RLO, anyway it has no meaning to you either.

• CDB exchanges a shared data block to an instance data block. Why do this?

• What is "LD 2"?

• What is "L#10000"?

• What is "DID 2"?

• What is "P#DBX 0.0"?

• Why are the "Call" and "End Call" commands in red?

• Is logic implemented in this manner for efficiency reasons?

• Can you briefly explain how to use AR1 and AR2?

This is a long story. In general, they are address registers used to address data.

The question you didn't ask: how did I get this mess?

So, the code in this place looked like this: 

CALL "FB 088 Template - Mtr", DB 502

(

input:=L#10000

)

But someone changed the interface of "FB 088 Template - Mtr", updated the DB 502 and downloaded only those two blocks without updating and downloading of the block which calls the "FB 088 Template - Mtr". So the consistency of the project was lost.

Later the whole program was uploaded from the CPU. The compiler found itself lost in this situation and did with the code what you can see now.

Hi j13s,

1. The called block in first row may not be properly compiled. Share the text in red. 

2. For UC or unconditional call, no parameter are passed. FB can not be used.

3. The remaining STL code is required to understand  logic. Pointer can't be understood with this info.

Thank you all. The explanation is very helpful. I now understand what caused these errors. My initial understanding was that somebody chose to program in this manner.

I will fix this to ensure that the next new person does not get confused as well.