Task $1$: Mealy Vend

The future is here. We can now buy miniature tacos from a vending machine, and they only cost $$\mathrm{.}15.$ Design a controller for this vending machine under these specifications:

Only one type of taco is available $($no user choice$)$

Only nickels $($$$\mathrm{.}05)$ and dimes $($$$\mathrm{.}10)$ are accepted

Only one coin can be entered at a time

Use a Mealy design, with J$-$K flip$-$flops

If the user pays extra, add that as credit for the next purchase $($e$.$g$.$ two dimes would provide one taco and $$\mathrm{.}05$ in memory$)$

Go through all five steps of the finite state machine design algorithm:

State diagram

Transition table $($for J$-$K flip$-$flop$)$

Next$-$state table

Derive Boolean equations $($make these simple by taking advantage of don$$t care conditions$)$

Implement and test circuit $($do this twice: once with LogicWorks chip schematics and once on the breadboard$)$

Do not forget to include the strobed D flip$-$flop at the output. Do you need a Not gate on its clock input? It depends on the edge behavior of your state memory $($J$-$K flip$-$flops$)$ and output signal $($D flip$-$flop$).$ They need to change half a clock cycle apart. Are the lab ICs positive$-$ or negative$-$edge triggered?

In report:

Thorough problem statement

Tables$/$figures and explanations for all steps of the design algorithm $($including the chip schematic circuit$)$

What happens when both coin inputs are active? Why did we not design for this?

Explain the purpose of the strobed D flip$-$flop for the output

Discuss how the Mealy design allows for storage of excess credit

Discuss abstraction in this design $($electrical signals$$binary codes$5$ cent increments$)$