Step 7 STL to LAD??

Why is it sometimes my STL will not convert to Ladder Logic?

Make a timer and don't fill in all in- out outputfields, convert to stl and you will see 'NOP 0' (no operation). Delete one or more 'NOP' and try to convert back to LAD. This will not go because Step7 needs this NOP to make the conversion.

Also some instruction are only possible in STL e.g. 'LAR'.

There a more things to watch out for but this takes more then a simple post to cover them all.

It doesn't have the required NOP 0's or the required BLD 0, BLD 7, BLD 8 and such to 'create' the LAD blocks.
Also if you do:

A #one
A #two
= #three
A #four
A #five
= #six

That won't convert, but if you split them up into 2 networks, it will.
Also the way brackets are used makes it sometimes impossible to convert, yet if put in correct order (not changing actual working of code ofc) it can convert.
The use of jumps immediatly eliminates the option.
Lots of ways to program in STL, yet only very few can be converted to LAD.

Best thing to learn what is possible is to rewrite your STL blocks in LAD where possible and then convert them to LAD, to see whats missing.

Jeebs said:

The use of jumps immediately eliminates the option.

Click to expand...

...actually you can jump in ladder using the LABEL instruction

...it's not very elegant though...

smcmanus said:

Why is it sometimes my STL will not convert to Ladder Logic?

Click to expand...

Can you give some specific examples of what you did to encounter this problem.