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# All VLSI programs

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• 1. LOGIC GATESmodule logic_gates(a,b,y1,y2,y3,y4,y5,y6,y7,y8); input a,b; output y1,y2,y3,y4,y5,y6,y7,y8; buf (y1,a); not (y2,a); or (y3,a,b); nor (y4,a,b); and (y5,a,b); nand (y6,a,b); xor (y7,a,b); xnor (y8,a,b);endmoduleHALF ADDER & FULL ADDERmodule half_adder(a,b,sum,carry); input a,b; output sum,carry; xor (sum,a,b); and (carry,a,b);endmodulemodule full_adder(a,b,c,sum,carry); input a,b,c; output sum,carry; assign sum = a^b^c; assign carry = (a&b)|(b&c)|(c&a);endmoduleHALF SUBTRACTOR & FULL SUBTRACTORmodule half_subtractor (x,y,difference,borrow);input x,y;output difference,borrow ;assign difference = (x^y), borrow =(~x&y);endmodulemodule full_subtractor (x,y,bin,d,bout);input x,y,bin;output d,bout;assign d = (x^y^bin), bout =(~x&y)|(~x&bin)|(y&bin);endmodule
• 2. PARALLEL ADDERmodule parallel_adder(a,b,cin,sum,cout);input [3:0] a,b;input cin;output [3:0] sum;output cout;assign {cout,sum}= a + b + cin;endmodulePARALLEL SUBTRACTORmodule parallel_subtractor(x,y,bin,difference,bout);input [3:0] x,y;input bin;output [3:0] difference;output bout;assign {bout,difference}= x - y - bin;endmoduleCARRY LOOK AHEAD ADDERmodule CLA_adder (a,b,cin,sum,cout);input [3:0]a,b;input cin;output[3:0]sum;output cout;wire po,p1,p2,p3,g0,g1,g2,g3;wire c1,c2,c3,c4;assign p0 = (a[0] ^ b[0]), p1 = (a[1] ^ b[1]), p2 = (a[2] ^ b[2]), p3 = (a[3] ^ b[3]);assign g0 = (a[0] & b[0]), g1 = (a[1] & b[1]), g2 = (a[2] & b[2]), g3 = (a[3] & b[3]);assign c0=cin, c1=g0 | (p0 & cin), c2 = g1 | (p0 & g0) | (p1 & p0 & cin), c3 = g2 | (p2 & g1) | (p2 & p1 & g0) | (p2 & p1 & p0 & cin), c4 = g3 | (p3 & g2) | (p3 & p2 & g1) | (p3 & p2 & p1 & g0) | (p3 & p2 & p1 & p0& cin);assign sum[0]=p0 ^ c0, sum[1]=p1 ^ c1, sum[2]=p2 ^ c2, sum[3]=p3 ^ c3;assign cout = c4;endmodule
• 3. PARALLEL ADDER & SUBTRACTORmodule parallel_add_sub( a3,a2,a1,a0,b3,b2,b1,b0,m,sum3,sum2,sum1,sum0,cout);input a3,a2,a1,a0;input b3,b2,b1,b0;input m;output sum3,sum2,sum1,sum0;output cout;wire cin,c0,c1,c2,d0,d1,d2,d3;assign cin = m;assign d0 = a0^m, d1=a1^m, d2=a2^m, d3=a3^m;full_add ff0(b0,d0,cin,sum0,c0);full_add ff1(b1,d1,c0,sum1,c1);full_add ff2(b2,d2,c1,sum2,c2);full_add ff3(b3,d3,c2,sum3,cout);endmodulemodule full_add(a,b,c,sum,carry); input a,b,c; output sum,carry; assign sum = a^b^c; assign carry = (a&b)|(b&c)|(c&a);endmodule8 :3 ENCODER & 3:8 DECODERmodule encoder8_to_3(d0,d1,d2,d3,d4,d5,d6,d7,a,b,c); input d0,d1,d2,d3,d4,d5,d6,d7; output a,b,c; or (a,d4,d5,d6,d7); or(b,d2,d3,d6,d7); or (c,d1,d3,d5,d7);endmodulemodule decoder3_to_8(a,b,c,d0,d1,d2,d3,d4,d5,d6,d7); input a,b,c; output d0,d1,d2,d3,d4,d5,d6,d7 ; assign d0 = (~a & ~b&~c), d1 = (~a & ~b&c ), d2 = (~a & b&~c ), d3 = (~a & b&c ), d4 = (a & ~b&~c ), d5 = (a & ~b&c ), d6 = (a & b&~c ), d7 = (a &b&c );endmodule
• 4. 1 :8 DEMULTIPLEXER & 4:1 MULTIPLEXERmodule demux1_to_8(i,s0,s1,s2,d0,d1,d2,d3,d4,d5,d6,d7); input i,s0,s1,s2; output d0,d1,d2,d3,d4,d5,d6,d7; assign d0 = (i & ~s2 & ~s1 & ~s0), d1 = (i & ~s2 & ~s1 & s0), d2 = (i & ~s2 & s1 & ~s0), d3 = (i & ~s2 & s1 & s0), d4 = (i & s2 & ~s1 & ~s0), d5 = (i & s2 & ~s1 & s0), d6 = (i & s2 & s1 & ~s0), d7 = (i & s2 & s1 & s0);endmodulemodule mux4_to_1(i0,i1,i2,i3,s0,s1,out); input i0,i1,i2,i3,s0,s1; output out; assign out = (i0 & ~s1 & ~s0)|(i1 & ~s1 & s0)|(i2 & s1 & ~s0)|(i3 & s1 & s0);endmodule8 BIT MULTIPLIERmodule multiplier_8_bit (a,b,c); input [7:0]a; input [7:0]b; output [15:0]c; assign c[15:0] = a[7:0]*b[7:0];endmoduleD FLIPFLOPmodule D_FF (D,clk,reset,Q); input D,clk,reset; output Q; reg Q; always @ (posedge reset or negedge clk)if (reset) Q = 1b0;else Q = D;endmodule
• 5. T FLIPFLOPmodule T_FF (T,clk,reset,Q); input T,clk,reset; output Q; wire w; assign w = T^Q; D_FF dff1(w,clk,reset,Q);endmodulemodule D_FF (D,clk,reset,Q); input D,clk,reset; output Q; reg Q; always @ (posedge reset or negedge clk)if (reset) Q = 1b0;else Q = D;endmoduleJK FLIPFLOPmodule JK_FF (J,K,clk,reset,Q); input J,K,clk,reset; output Q; wire w; assign w = (J&~Q)|(~K&Q); D_FF dff1(w,clk,reset,Q);endmodulemodule D_FF (D,clk,reset,Q); input D,clk,reset; output Q; reg Q; always @ (posedge reset or negedge clk)if (reset) Q = 1b0;else Q = D;endmodule
• 6. SYNCHRONOUS UP-DOWN COUNTERmodule updown_counter(up_down,clk,reset,count);input [1:0]up_down;input clk,reset;output [2:0]count;reg[2:0]count;always @(posedge clk or posedge reset)if (reset==1)count<=3b000;elseif(up_down==2b00 ||up_down ==2b11)count<=count;elseif(up_down==2b01)count<=count+1;elseif(up_down==2b10)count<=count-1;endmoduleUNIVERSAL SHIFT REGISTERmodule unishft_reg(s1,s0,PIin,LFin,RTin,clk,reset,q3,q2,q1,q0);input s1,s0; // select inputsinput LFin,RTin; // serial inputsinput clk,reset;input[3:0]PIin; // parallel inputoutput q3,q2,q1,q0; // register outputreg q3,q2,q1,q0;always @ (posedge clk or posedge reset)if (reset){q3,q2,q1,q0}=4b0000;elsecase ({s1,s0}) 2b00:{q3,q2,q1,q0}={q3,q2,q1,q0}; // No change 2b01:{q3,q2,q1,q0}={RTin,q3,q2,q1}; // Shift right 2b10:{q3,q2,q1,q0}={q2,q1,q0,LFin}; // Shift left 2b11:{q3,q2,q1,q0}=PIin; // Parallel load inputendcaseendmodule
• 7. CMOS INVERTERmodule my_inv(in,out);input in;output out;supply1 pwr;supply0 gnd;pmos ( out,pwr,in);nmos (out,gnd,in);endmoduleCMOS NOR GATEmodule my_nor(a,b,out);input a,b;output out;wire c;supply1 pwr;supply0 gnd;pmos ( c,pwr,b);pmos (out,c,a);nmos(out,gnd,a);nmos(out,gnd,b);endmoduleCMOS NAND GATEmodule my_nand(a,b,out);input a,b;output out;wire c;supply1 pwr;supply0 gnd;pmos ( out,pwr,a);pmos (out,pwr,b);nmos(out,c,a);nmos(c,gnd,b);endmodule
• 8. SR FLIPFLOPmodule sr_flipflop(s,r,clk,q,qbar);input s,r,clk;output q,qbar;reg q,qbar;always@(posedge clk)begin case ({s,r}) 2b00:q=q; 2b01:q=1b0; 2b10:q=1b1; 2b11:q=1bx; endcase qbar=~q; end endmoduleCMOS XOR GATEmodule my_xor(a,b,out);input a,b;output out;wire e,f,g;supply1 pwr;supply0 gnd;assign c=~a;assign d=~b;pmos (e,pwr,c);pmos (e,pwr,d);pmos (out,e,a);pmos (out,e,b);nmos(out,f,a);nmos(f,gnd,b);nmos(out,g,c);nmos(g,gnd,d);endmodule