force-step-instruction command will refuse to run if the processor is stalling.
The -n flag tells the command to switch to the next processor in the scheduling list of the cell after each instruction.
With the -r flag, register changes are printed after every step.
The -q flag tells the command not to disassemble the executed instruction.
Since the force-step-instruction command changes the default scheduling order of processors, the same execution path will not be followed if the simulation is rerun using reverse execution for example.