Hello macs_plc;
PLCSim is a software emulator that works in combination with Step 7. It simulates memory areas of a PLC so you can test a program or function blocks without downloading to a hardware controller.
Now, whether this controller is (or will eventually be) a S7-300 CPU, a C7 CPU + HMI, a slot PLC or a soft PLC is irrelevant...
Hope this helps,
Daniel Chartier