Advanced Digital Circuits ECET 146 Week 9 Professor Iskandar Hack ET 221B,

This Week’s Goals Assignment of short project – without specific instructions on completing project. Goal of this project is to force the student to review all of the previous labs and examples to determine a way to solve the design problem. This is the last lab prior to the final project, so consider this lab a warm up to the final project. Thus the amount of guidance provided for this lab will be minimal. The TA and myself will only answer specific questions and aid in determining the source of errors. But the student is expected to do this lab pretty much without guidance.

Vending Machine Specification You will design the simplest (and probably the least practical) vending machine on the planet. This Vending machine will only accept quarters and dispense only one product, we’ll call it ECET-Cola. The cost of the product of ECET-Cola is one dollar or 4-quarters After receiving four quarters the Vending Machine will take the dispense signal high for one clock cycle The Vending Machine will also have a refund mode – that will take the refund signal high for the number of clock cycles that equate to the number of quarters entered After either vending or dispensing a can of ECET-Cola the vending machine will return to the idle mode The next slide shows a possible bubble graph, but there are other solutions

Vending Machine Bubble Graph

Report Requirements Simulate the machine’s operation, but you do not have to implement in hardware. You do not need to ‘demonstrate’ this project only turn in the report. Turn in a ‘short or informal lab’ report. That is only the design files and a COMPLETE simulation. The simulation should cover the situations that both product is vended and several refund scenarios.

Some Hints In state the transition from states S0, S1, S2, and S3 to the next state increment the count to keep track of the number of quarters to refund if the input refund is pressed. You’ll need to use an array of flip-flops for this, look at the earlier example for a counter. Take the output Vend high during the SVEND state and Low during all others. Take the output RETURN high during the SREFUND state and Low during all others. Decrement count each clock cycle during the state SREFUND, and use an IF statement to determine if enough quarters have been refunded.