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Spring_05_Project - • The controller does not give any...

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Spring 2005 COCO Project Description and Specifications Description and Specifications 1. Description of the Vending Machine The vending machine delivers a package of goodies after it has received 25¢ or more in coins. The machine has a single coin slot that accepts only nickels, dimes and quarters, one at a time – no pennies. The block diagram of the controller is shown here. A Coin Sensor device indicates to the Controller whether a nickel, dime or quarter has been inserted into the coin slot. A Coin Dispenser device returns any coins held; otherwise, the coins go into a Coin Box. This is shown at the bottom of the page. 2. S p ecifications for the Vending Machine Controller Q or D or N is true for one clock period when a Q or D or N is inserted into the coin slot. A package of goodies is dispensed only once 25¢ or more has been deposited. The controller does not give any change. For example, if the coins inserted are
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Unformatted text preview: • The controller does not give any change. For example, if the coins inserted are N, D, N, D, totaling 30¢, the controller does not return the extra 5¢. • The controller does apply the extra amount deposited (5¢ in the example) as a credit to the next user. Only 20¢ needs to be inserted to obtain the next package of goodies. • The input Coin_return is active for one clock period. This activates the Return_coins output. The Return_coins output is asserted only when there is less than 25¢ credit in the machine. (The Coin Dispener device returns any coins that have been deposited since the last time Dispense_goodies was asserted.) Q D N Coin_return Clock VENDING MACHINE CONTROLLER Dispense_goodies Return_coins COIN SENSOR Single Coin Slot Q D N COIN DISPENSER Dispense_goodies Return_coins All Deposited Coins Returned Coin Box...
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