Final Exam ProjectFinal Exam Project

4 bit Full Adder Layout and Analysis using Lasi and WinSpice

Assignment ObjectivesAssignment Objectives

Do a hierarchal layout of a half adder, full adder and 4 bit adder using LASI, then simulate the circuit using SPICE to make sure that the design will work.

OverviewOverview

Hierarchal Layout design is done using Lasi.

N3X2, P3X2, NAND, XOR, Half-Adder, Full-Adder and 4 bit Full Adder layouts are made in hierarchal sfashion using bottom up approach.

Each Cell is analyzed by using Winspice3 .CIR file created by Lasi.

P3X2 (Rank 1)Cell- Standard cell from Lasi P3X2 (Rank 1)Cell- Standard cell from Lasi LibraryLibrary

N3X2 (Rank 2) Cell -Standard cell from Lasi N3X2 (Rank 2) Cell -Standard cell from Lasi LibraryLibrary

INVERTER (Cont’d)INVERTER (Cont’d)

Inverter cell has Rank 2. Inverter cell is made using

P3X2 and N3X2 cell. It is used to provide A’ and B’

for XOR input and NAND input to make OR gate.Also it is used at output of a NAND to make AND.

INVERTERINVERTER

NAND (Cont’d)NAND (Cont’d)

NAND cell has rank 2. It is used to make AND gate and OR

gate.

NANDNAND

XOR (Cont’d)XOR (Cont’d)

XOR cell has Rank 2. It is is made to provide sum of Half Adder.It is little different than regular XOR because it requires four inputs A, A’, B, and B’. By designing in with four inputs we simplify design and reduced transistors.

XORXOR

Half-Adder (Cont’d)Half-Adder (Cont’d)

Half-Adder has rank 3. It is designed using INVERTER, NAND and XOR gate. Sum = AB’ + B’A. Carry = AB.

Half-AdderHalf-Adder

Full-Adder (Cont’d)Full-Adder (Cont’d)

It has rank 4. Full adder is made using two HALF-ADDER , 2 Inverter and a NAND gate. S1 = HA(A,B) Sum = HA(S1,Carry In)Carry = OR(Carry 1,Carry 2)

Full-AdderFull-Adder

4 Bit Full Adder (Cont’d)4 Bit Full Adder (Cont’d)

It has rank 5. It is made using four 1 bit Full-Adder. First Full-Adder has Carry in 0. 4th Carry out is Final Carry out of 4 bit Full-

Adder.

4 Bit Full Adder4 Bit Full Adder

SPICE SIMULATIONSPICE SIMULATION

Each cell is compiled using LasiCkt. Generate .CIR files used in WinSpice3 for

simulation of circuit. Every analyzed signal is offset by 6V to

see each signal properly.

INVERTER Simulation (Cont’d)INVERTER Simulation (Cont’d)

Next slide shows screen capture of Inverter simulation.

A_ is output of signal input signal A.

INVERTER SimulationINVERTER Simulation

NAND Simulation (Cont’d)NAND Simulation (Cont’d)

Next slide show simulation of NAND gate.

AB_ is output of NAND gate. 11,10,01,00 signals analyzed.

NAND SimulationNAND Simulation

XOR Simulation (Cont’d)XOR Simulation (Cont’d)

Next slide show simulation of XOR gate.

AXORB is output of XOR gate. 11,10,01,00 signals analyzed. It is Sum of Half-Adder.

XOR SimulationXOR Simulation

Half-Adder Simulation (Cont’d)Half-Adder Simulation (Cont’d)

Next slide show simulation of Half-Adder gate.

S is Sum and C is carry. 11,10,01,00 signals analyzed.

Half-Adder SimulationHalf-Adder Simulation

Full-Adder Simulation(Cont’d)Full-Adder Simulation(Cont’d)

Next slide show simulation of full adder. All the combination from 000 to 111 is used as Cin, B and A inputs.

Full-Adder SimulationFull-Adder Simulation

4 Bit Full Adder Simulation (Cont’d)4 Bit Full Adder Simulation (Cont’d)

Next four slides shows simulation of 4 bit Full Adder.

Individual plot used each inputs for proper demonstration.

VN4 is Carry out 1. VN5 is Carry out 2. VN6 is Carry out 3.

4 Bit Full Adder Simulation- A0+B0 (Cont’d)4 Bit Full Adder Simulation- A0+B0 (Cont’d)

4 Bit Full Adder Simulation- A1+B1 (Cont’d)4 Bit Full Adder Simulation- A1+B1 (Cont’d)

4 Bit Full Adder Simulation- A2+B2 (Cont’d)4 Bit Full Adder Simulation- A2+B2 (Cont’d)

4 Bit Full Adder Simulation- A3+B3 (Cont’d)4 Bit Full Adder Simulation- A3+B3 (Cont’d)

Related DocumentsRelated Documents

Included floppy contains two directories LASI and CIR. LASI Directory Contains all the Layout files and other

required files to open layouts in LASI . To open LASI Layout files create shortcut of LASI

executable file, and change the “Start in” option through properties to A:\ LASI \.

Circuit simulation .CIR files are located in CIR directories.