EGR 270 Fundamentals of Computer Engineering File N270L3 Lab 3 Combinational Logic Circuits and 7 Segment Displays Lab Format A This is a Individual Lab so each student must design and test their own circuits Students are free to assist each other in all labs Each student must complete the Preliminary Work Section before lab begins Preliminary Work will be checked in lab and will be part of the lab report grade Each student must submit his or her own lab report Lab reports will not be accepted until all required circuits have been demonstrated to the instructor Objective The objective of this laboratory is to investigate the design procedure for combinational logic circuits discussed in class and to use the design procedure to design and build a custom combinational logic circuit Some commonly used combinational logic functions are already available commercially and do not have to be designed from scratch An example is a BCD to 7 segment decoder In this lab a 7 segment display will be driven using a commercially available BCD to 7 segment decoders B Materials Breadboard 5V Power Supply Wire switches resistors etc Common anode 7 segment display GNS 3011 LDS3221 MAN72A or other 74LS47 BCD to 7 segment decoder driver common anode 74LS00 74LS02 74LS04 74LS08 74LS32 and 74LS86 IC s C Introduction Combinational logic circuits can be divided into two categories 1 Custom circuits Unique circuits where there is no commercially available device In this case the design procedure for combinational logic circuits can be used 2 Commercially available devices Including decoders encoders multiplexers BCD to 7 segment decoders magnitude comparators etc Note that the general design procedure could be used to design these devices but it is unnecessary and the commercial devices are often optimized for reduced delay Design Procedure for combinational logic circuits 1 Specification Write a specification for the circuit if one is not provided 2 Formulation Derive the truth table or initial Boolean equations that define the required relationships between inputs and outputs 3 Optimization Apply two level and multiple level optimization using Karnaugh Maps or Boolean algebra Draw a logic diagram or provide a netlist using AND OR and NOT gates 4 Technology Mapping Implement the circuit using the desired technology such as using AND OR NOT gates decoders multiplexters PLDs FPGA etc 5 Verification Verify the correctness of the circuit perhaps by hand analysis or computer simulation Example See examples of the design procedure in the class notes 1 BCD to 7 segment decoders Since BCD to 7 segment decoders are commercially available we don t need to design them using the design procedure Recall from class notes that there are two types of BCD to 7 segment decoders a Common cathode decoder Uses active HIGH outputs i e a HIGH output is used to light a segment Must be used with a common cathode 7 segment display Example 74LS48 See Figure 1 below b Common anode decoder Uses active LOW outputs i e a LOW output is used to light a segment Must be used with a common anode 7 segment display such as the GNS 3011 or LDS 3221 Example 74LS47 we will use this type in lab See Figure 2 below D C B A LSB Figure 1 7448 and a common cathode 7 segment display D C B A LSB Figure 2 7447 and a common anode 7 segment display 2 D Preliminary Work Include instructions with each step in your report 1 7 segment display and decoder circuit A Generate a logic diagram using PSPICE for Circuit 1 including 7 segment display check with the instructor to see which part will be used in lab o If the MAN72A or LDS3221 is to used in lab the following part can be used in PSPICE since it has the same pinout LDS A30R in the Discrete Library Note that the Discrete Library is not part of the evaluation version so you can t analyze circuits with this component o If the GNS 3011 is to be used in lab the following part can be used in PSPICE since it has the same pinout LDS A32R in the Discrete Library 7447 BCD to 7 segment decoder or the 7446 if it is not available since it has the same pinout Input switches DIP switches resistors etc Be sure to label the switches A B C D No PSPICE simulation is required simply draw the schematic Add text to the schematic name course lab number title of circuit etc Dip Switches D C B A LSB Circuit 1 Testing the 7447 and a common anode 7 segment display B C D Check the data sheet for the 7447 see course website to determine the function of LT BI RBO RBI Write out a clear description of each in your own words Show how to connect four 7447 IC s using a simple block diagram such that leading zeros will not be displayed for example the displays will show blank 607 rather than 0607 Check the data sheet for the 7447 to determine the pattern that is lit on the 7 segment display for each of the 16 possible inputs Illustrate the results with sketches or copy them from the data sheet continued on next page 3 2 Student ID Conversion Circuit Use the design process to design a combinational logic circuit that will convert the digits 0 6 to the 7 digits in your student ID It should also convert the digit 7 to a 9 For example if your student ID is 1302477 then the circuit should make the following conversions 0 1 1 3 2 0 3 2 4 4 5 7 6 7 7 9 In particular include the following A List the numbers to be converted using your Student ID similar to the boxed section above B Draw a truth table Note that there should be 3 inputs and 4 outputs C Form minimal SOP and POS expression using Kmaps D If the circuit is to be implemented using any of the following types of logic gates determine the fewest number of gates possible Consider SOP POS gate sharing XORs etc 7400 2 input NAND 7404 NOT 7402 2 input NOR 7408 2 input AND 7432 2 input OR 7486 2 input XOR E Generate a Logic Diagram using PSPICE for Circuit 2A including Show assigned chip numbers and part numbers For example U1 7447 Be sure to use all available gates on a given IC before using another IC of the same type e g using U1A U1B U1C etc instead of U1A U2A U3A etc Use 3 digital clocks in PSPICE for inputs A B and C Do not show DIP switches even though we will use them in lab Label all inputs and outputs Label MSB on the input and the output Do not include the 7447 and 7 segment display even though we will connect them to the output in lab D A BCD to E Digital B Student F Clocks C ID Converter G Circuit 2A BCD to Student ID Converter PSPICE Circuit F Extra Credit 10 pts on lab grade Simulate