1. LOGIC GATES

In VLSI Gates are the building blocks of the circuit.They are seven types of gates which is applicable.

• AND 
• OR
• NOT
• NAND
• NOR
• EXOR
• EXNOR
• BUFFER

Here NAND and NOR gates are called Universal gates.From this gates we can able to construct many logic circuits. Here in this for VLSI Implementation  Hardware Description languages like Verilog and VHDL are used.

For example let us see the example of AND Gate:

AND GATE:

PROGRAM;

module and ( a ,b ,y );

output dout ; 

input a ; 

input b ; 

assign y = a & b; 

endmodule

OUTPUT WAVEFORM FOR AND GATE 

Hence the program and Implementation of all gates in one circuit

PROGRAM

 module logic1 ( a ,b ,c ,d ,e ,f ,g ,h ,i ,j ); 

output c ; 

output d ; 

output e ; 

output f ; 

output g ; 

output h ; 

output i ; 

output j ; 

input a ; 

input b ; 

assign c = a & b; 

assign d = a | b; 

assign e = ~a; 

assign f = ~b; 

assign g = ~(a & b); 

assign h = ~(a | b); 

assign i = a ^ b; 

assign j = a ^~ b; 

endmodule

OUTPUT WAVEFORM

In next session we can see the types of adders and all other circuits