lab5_f11_Debouncing_Counter - University of Florida...

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University of Florida EEL 3701 — Fall 2011 Dr. Eric M. Schwartz Department of Electrical & Computer Engineering Revision 0 5-Oct-11 Page 1/3 LAB 5: A Debounced Switch and Counters Figure 1 : Simple counter block diagram. OBJECTIVES To understand the design, function and operation of a debounced switch and simple counter circuits. MATERIALS Your entire lab kit Suggested Quartus Components In “others | maxplus2” library o 7474: Dual D-flip flops In “primitives | storage” library o dff In “primitives | logic” library o not, and2, or2, bor2, etc. In “primitives | pin” library o input, output In “primitives | other” library o vcc, gnd Bring your printouts from lab 4 to this lab: UF-3701 Programming WARNING ! 7064 Pin Definitions MAX 7000 specification sheet INTRODUCTION NOTES ON UF-3701 BOARD AND QUARTUS The ground connection is the most important one for the UF-3701 board. Connect the ground pin (labeled G on your UF-3701 board) to the ground on your breadboard. Similarly, connect the power pin (labeled 5V on your UF- 3701 board) to the power on your breadboard. Be very careful that you do NOT reverse these pins; if you do, the chip will be destroyed and you will need to buy a new one. (See the website for information on purchasing a new CPLD.) Pin 43 on your UF-3701 board should generally be selected for your clock input. This is a global clock pin. Pin 2 may also be used. DEBOUNCED SWITCHES The switches that you have been using this semester are know as single-pole-single-throw (SPST) switches. When you move the SPST switch in a switch circuit from ON to OFF or from OFF to ON, the resulting output bounces around between low and high voltages for a short time. If the switch circuit output is used as a synchronizing signal (such as a clock) in a digital machine, weird things will happen. If the machine is a counter, the count may seem to jump wildly. This is obviously undesirable, so a debouncing circuit must be built. We discussed several debouncing circuits in class. You will design and build one of these debounced switch circuits using a single-pole-double-throw (SPDT) switch. You will use this debounced switch circuit in this lab and rest of the labs this semester. The SPDT switch has three aligned pins. The center pin is connected to one or the other of the outside pins, depending on the position of the switch. You can use your multimeter on the resistance ( ) setting to verify the operation of this switch. There are two pins on the switch in addition to the three aligned pins. These two pins have no useful electrical purpose and are used for mounting only. These pins are electrically connected to the center pin of the three aligned pins, and thus must be removed , i.e., carefully bent or broken off of the device. (If these two pins are not removed, when the switch is plugged into a breadboard, the switch will have no effect.) COUNTERS A synchronous counter is a device that progresses through
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lab5_f11_Debouncing_Counter - University of Florida...

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