Question

Digital electronics
in the exam assignment, I should  construct a wheelchair lift and it would be controlled by a combinatorial network type mealy. the combinatorial network should control an electric motor that drives the lift up and down. The lift is controlled by a power button (elevator button) =x_2. when the elevator is down and you press x_2 motor starts and goes up and vice versa if you are up. at the end positions, there are mounted two switches x_1 and x_0 to be shut down the engine when the elevator has reached the end position

Answer 1

x_2 gives a logic 1 if you press the button, otherwise a 0
x_1 gives a logic 1 if the lift is down otherwise a 0
x_0 gives a logic 1 if the lift is up otherwise a 0

two output signals:
u_1 and u_0

if u_1 and u_0 = 0 0 the engine(the lift) isnt moving
if u_1 and u_0 = 1 0 the lift goes up
if u_1 and u_0 = the lift goes down

And then we have some delimitations
the lift only have two floors. We assume that the lift is always down at start. And ofcourse there is a emergencybutton but we take no accounts of that one

Solution:
Code with gray-code. The task gives 3 inputvariables and 2 state variables. is solved 2 karnaughdiagram. Let x_2 seperate the diagrams. solve it with NOR-gates for D-flipflop. the schedual doesnt have to be drawn