ECE281_CE3

##Elevator Controller VHDL code and testbench that simulates an elevator controller that traverses 4 floors ####Moore Machine Implementaion of elevator controller as a Moore Machine, the output only depends on the state in a Moore Machine. ######Code Design Began with the given shell, goal was to edit the process that defined the floor state. There was an inefficent piece of code found in the given shell.

clk'event and clk='1'

was changed to

RISING_EDGE(CLK)

The if statements were then filled in.

				when floor3 =>
					if (up_down='0' and stop='0') then 
						floor_state <= floor2;
					elsif (up_down='1' and stop='0') then 
						floor_state <= floor4;	
					else
						floor_state <= floor3;	
					end if;
				when floor4 =>
					if (up_down='0' and stop='0') then 
						floor_state <= floor3;	
					else 
						floor_state <= floor4;
					end if;

Also had to define the output logic, in a Moore Machine, the output logic only depends on the state.

floor <= "0001" when (floor_state = floor1) else
			"0010" when (floor_state = floor2) else
			"0011" when (floor_state = floor3) else
			"0100" when (floor_state = floor4) else
			"0001";

#####Testbench The testbench implemented a for loop to traverse through all 4 levels of the elevator, to change levels up, up_down was kept at 1 and stop was changed with the clock.

for i in 1 to 4 loop
	wait for clk_period*2;				
	assert(floor = floorNum ) report "FAIL! Current Floor is"&integer'image(to_integer(unsigned((floor)))) severity note;
	assert(floor = floorNum-1 ) report "SUCESS! Current Floor is"&integer'image(to_integer(unsigned((floor)))) severity note;
	stop <= '0';
	up_down <= '1';
	wait for clk_period*2;
	stop <= '1';
	floorNum <= floorNum + "0001";
end loop;

The testbench results show that the elevator starts at level 1 (0001) and rises a level and waits at that level for 2 clock periods everytime the stop becomes 0. When the elevator reaches level 4 (0100), it descends back to 1. The self-checker explicitly shows the change in levels.

####Mealy Machine Implementaion of elevator controller as a Mealy Machine ######Code Design The only difference in the Mealy Machine is the output logic. To implement this in VHDL some rearranging had to be done.

floor <= "0001" when (floor_state = floor1) else
			"0010" when (floor_state = floor2) else
			"0011" when (floor_state = floor3) else
			"0100" when (floor_state = floor4) else
			"0001";
nextfloor <= 	"0001" when (floor_state = floor1) and (stop = '1') else
					"0010" when (floor_state = floor2) and (stop = '1') else
					"0011" when (floor_state = floor3) and (stop = '1') else
					"0100" when (floor_state = floor4) and (stop = '1') else
					"0010" when (floor_state = floor1) and (up_down = '1') and (stop = '0') else
					"0011" when (floor_state = floor2) and (up_down = '1') and (stop = '0') else
					"0100" when (floor_state = floor3) and (up_down = '1') and (stop = '0') else
					"0100" when (floor_state = floor4) and (up_down = '1') and (stop = '0') else
					"0001" when (floor_state = floor1) and (up_down = '0') and (stop = '0') else
					"0001" when (floor_state = floor2) and (up_down = '0') and (stop = '0') else
					"0010" when (floor_state = floor3) and (up_down = '0') and (stop = '0') else
					"0011" when (floor_state = floor4) and (up_down = '0') else
					"0001";  --phantom state

#####Testbench The testbench for the Mealy machine is the same as the Moore with slightly different self-checker.

for i in 1 to 4 loop
				wait for clk_period*2;				
				assert(floor = floorNum ) report "FAIL! Current Floor is"&integer'image(to_integer(unsigned((floor)))) severity note;
				assert(floor = floorNum-1 ) report "SUCCESS! Current Floor is"&integer'image(to_integer(unsigned((floor)))) severity note;
				stop <= '0';
				up_down <= '1';
				wait for clk_period;
				if (floorNum < "0100") then
				assert(nextfloor = floorNum+1) report "FAIL! Next Floor is"&integer'image(to_integer(unsigned((nextfloor)))) severity note;
				end if;
				assert(nextfloor = floorNum) report "SUCCESS! Next Floor is"&integer'image(to_integer(unsigned((nextfloor)))) severity note;
				wait for clk_period;
				
				stop <= '1';
				floorNum <= floorNum + "0001";
			end loop;			
			
			stop <= '0';
			up_down <= '0';
			wait for clk_period*6;			
			assert(floor = "0000") report "SUCCESS! Current Floor is"&integer'image(to_integer(unsigned((floor)))) severity note;

The testbench results show that the elevator starts at level 1 (0001) and rises a level and waits at that level for 2 clock periods everytime the stop becomes 0. When the elevator reaches level 4 (0100), it descends back to 1. The self-checker explicitly shows the change in levels. The next level is also shown corectly by the self checker.

###Debugging I forgot that binary numbers need to have quotes around them to be interpreted properly. It took a little while to find the right place between clock changes to put my assert statements. ###Questions Moore: is reset synchronous or --asynchronous?
     -synchronus, changes with the clock.
Mealy: is reset synchronous or --asynchronous?
     -synchronus, dependent on clock as well.
What is the clock frequency?
    -1/10ns 100MHz, freq = 1/period
What value would we set to simulate a 50MHz clock?
    -1/t = 50,000,000, 20ns
If up_down is set to "go up" and stop is set to "don't stop" which floor do we want to go to?
    The next floor up, untill the max floor is reached in which case the floor doesn't change.
####Documentation C3C Tyler Spence helped be realize that a Mealy machine is dependant on both the state and the input.