Q$21.$ You will design a circuit to control the speed of a step motor. Speed is a $4-$bit value between $0$

and $15$ controlled with two buttons $($UP and DOWN buttons$).$ Initially, the speed must be set

to zero upon reset. In your design, you can use only the $4-$bit Up$/$Down counter given below

and logic gates. Sketch a circuit schematic of your design and write the necessary truth tables

and Boolean equations to show your work. You should use the minimum amount of hardware.

If no button is pushed, no change in speed occurs.

Up$-$button increments the speed by one. When the speed value is maximum, it will not be

increased anymore $($the speed value will not wrap around from $1111$ to $0000).$

Down$-$button decrements the speed by one. When the speed value is minimum, it will not

be decreased anymore $($the speed value will not wrap around from $0000$ to $1111).$

If both buttons are pushed, no change in speed occurs.