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Tutorial 3

# Tutorial 3 - Elec 151 Tutorial#3 Outline Lab 3 Orcad Logic...

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Elec151 - Tutorial #3 1 Elec 151 Tutorial #3 Outline: Lab 3: Orcad Logic Simulation Karnaugh Maps (K-Map) - Sum of Products (Minterms) - Product of Sums (Maxterms) - K-Map Method • Problems Elec151 - Tutorial #3 2 (a) Prelab Design a “4-bit Magnitud Comparator circuit ” based on the “Adder-Subtractor” used in Lab 2 that compares A and B. How should I modify the circuit? Note: the circuit must provide 3 outputs: x, y and z (If A=B , then the output x=1 . If A<B , then the output y=1 . If A>B , then the output z =1 ). Lab 3: Orcad Logic Simulation 4-bit Adder- Subtractor A(4:1) B(4:1) CARRY S(4:1) M x (A=B) y (A<B) z (A>B) 4-bit Magnitud Comparator Elec151 - Tutorial #3 3 Analyzing the “4-bit Comparator”: We do comparison by doing subtraction (A+2’s complement of B) and analyzing the result (i.e. analyzing C 4 and S(4:1)). … (a) Prelab C 4 S 4 S 3 S 2 S 1 x (A=B) y (A<B) z (A>B) 1 0 0 0 0 1 0 0 1 Not Zero 0 0 1 0 Not Zero 0 1 0 0 0 0 0 0 Will never happen C 4 (CARRY ) S 4 S 3 S 2 S 1 x (A=B) y (A<B ) z (A>B) Don’t care 0 0 0 0 1 0 0 1 Not Zero 0 0 1 0 Don’t care 0 1 0 From this table, we can find out the gates to be used in the final circuit. e.g. __ 1 __ 2 __ 3 __ 4 S S S S x = Elec151 - Tutorial #3 4 Main steps 1. Create a PSpice Netlist: (Tools ->Create netlist ->Pspice). 2. Generate the stimuli (input vectors): (Place part -> Source -> STIM1 -> drag, place & connect to A[1:4]) (b) Main Steps for the 4-bit Adder - Subtractor U2A 74LS86A 1 2 3 S1 DSTM4 B3 A4 S1 DSTM8 A1 S1 DSTM2 U2B 74LS86A 4 5 6 S1 DSTM5 S1 DSTM3 S1 DSTM9 U2C 74LS86A 9 10 8 B2 A3 S1 DSTM6 U2D 74LS86A 12 13 11 A Title Size M S1 DSTM7 B1 A2 B4 U1 74LS83A 1 3 8 10 16 4 7 11 13 14 15 2 6 9 A4 A3 A2 A1 B4 B3 B2 B1 C0 C4 SUM4 SUM3 SUM2 SUM1 S1 DSTM1

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Elec151 - Tutorial #3 5 … Main steps 3. Enter stimuli: (Double click in DSTMx -> Enter the stimuli in Command 1, 2, 3, …) Stimulus: DSTM9 DSTM8 DSTM7 . . . DSTM1 Signal: M B4 B3 . . . A1 COMMAND1 0ns 0 0ns 0 0ns 0 . . . 0ns 0 COMMAND2 650ns 1 100ns 1 300ns 0 500ns 1 800ns 0 1100ns 1 100ns 1 . . . 200ns 1 COMMAND3 300ns 0 500ns 1 800ns 0 1100ns 1 . . .
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Tutorial 3 - Elec 151 Tutorial#3 Outline Lab 3 Orcad Logic...

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