An S7-1500 migration from a CPU 315-2 PN/DP: the two migrations, the four message classes in the TIA Portal log, and the STL that comes back marked.
Analogue scaling in STL on an S7-300, S7-400 or S7-1500: multiply before you divide, mind the DINT ceiling, and check OS rather than OV after the chain.
A PLC FOR-DO loop in structured text that walks a barcode array with SIZE and hands back the index where the value sits, or nothing if it is absent.
Which PLC programming software to learn first, why ladder and STL come before the rest, and how reading other people’s programs speeds it up.