Moving from RSLogix 500 to Studio 5000: what actually changes?

The instruction set is largely familiar. The data model is not, and that is where the time goes. In SLC and MicroLogix, addresses are physical: N7:0, B3:0/2, T4:1. The address tells you where the value lives. In ControlLogix you have named tags with data types, and the physical address only appears at the I/O module. Everything else is a name. What that changes in practice: - Arrays and UDTs replace address arithmetic. A 20 element structure is one tag, not a block of N7 you have to remember the layout of. - Timers become TIMER structures with .PRE, .ACC, .DN. No more T4:1/DN. - Add-On Instructions replace copy and paste. Worth learning early, because most SLC programs are full of repeated logic that becomes one AOI. - Aliases let you name a physical point once and use the name everywhere. The conversion tool will produce something that runs, and it will be full of N7_0 style tags that carry none of that benefit. It is a starting point, not a finished migration. Budget time to re-tag it properly or you have moved the program without gaining anything.