Can a slc 5/03 be used as a direct replacement for a slc 5/03? In other words, can I just slide the 5/02 out, slide the 5/03 in, load the program and go?
You will have to change the controller type in RSLogix 500, and set the DH485 Node Number in the Channel 1 Configuration.
But that's about it; the SLC-5/03 has instructions and features that the SLC-5/02 doesn't, but all the instructions and status registers and other operations of the 5/02 are forward-compatible.