LDMicro created by Jonathan Westhues is nice free program which can turn any PIC or AVR microcontroller in PLC with ladder logic.
The list of the supported devices is:
- PIC16F628(A), PIC16F88, PIC16F819, PIC16F877(A), PIC16F876(A), PIC16F887, PIC16F886
- ATmega128, ATmega64, ATmega162, ATmega32, ATmega16, ATmega8
LDmicro allow you to make your ladder schematic then to generate HEX code which does the ladder logic implementation in program code which you program to your AVR or PIC and got the ladder logic functionality.
LDmicro have interfaces in 7 languages, here is nice tutorial how to use it
Forum is available where you can ask for help if something doesn’t work as expected
LDmicro adds nice functionality to PIC-IO and MOD-IO, AVR-IO, AVR-IO-M16 and offer yet another option to program these boards.