Hello Dear Readers, Today in this post, I will provide some deep insight into the Signal Electromigration (Signal EM): Violations, Examples, and Practical Fixes. 1. Introduction: As technology nodes shrink into the deep‑submicron and nanometer regime (7nm, 5nm, 3nm and beyond), electromigration (EM) has become a first‑order reliability concern—not only for power/ground (PG) networks but also for signal nets. Signal EM failures are often underestimated because signal currents are transient and bidirectional. However, with higher switching activity, tighter metal pitches, thinner wires, and aggressive timing closure, signal EM can cause latent or early‑life failures if not addressed properly. This article explains: What Signal EM is and how it differs from PG EM Typical Signal EM violation scenarios Detailed, practical examples Root causes behind each violation Proven solutions and best practices to fix and prevent Signal EM issues 2. What is Signal Electromigration: El...
Hello Dear Readers,
Today In this post I have designed a carry-lookahead adder design and implemented its parametrized version using Verilog HDL and analysis that design for the desire output. First of all, I have designed CLA based on the theory described in the below video of the Neso Academy.
Verilog Code:
module add (a, b, c, g, p, s); // adder and g, p
input a, b, c; // inputs: a, b, c;
output g, p, s; // outputs: g, p, s;
assign s=a ^ b ^ c; // output: sum of inputs
assign g = a & b; // output: carry generator
assign p = a | b; // output: carry propagator
endmodule
module gp (g,p,c_in,g_out,p_out,c_out); // carry generator, carry propagator
input [1:0] g, p; // lower level 2-set of g, p
input c_in; // lower level carry_in
output g_out,p_out,c_out; // higher level g, p, carry_out
assign g_out = g[1] | p[1] & g[0]; // higher level carry generator
assign p_out = p[1] & p[0]; // higher level carry propagator
assign c_out = g[0] | p[0] & c_in; // higher level carry_out
endmodule
module cla_2 (a, b, c_in, g_out, p_out, s); // 2-bit carry lookahead adder
input [1:0] a, b; // inputs: a, b
input c_in; // input: carry_in
output g_out, p_out; // outputs: g, p
output [1:0] s; // output: sum
wire [1:0] g, p; // internal wires
wire c_out; // internal wire
// add (a, b, c, g, p, s); // generates g,p,s
add a0 (a[0], b[0], c_in, g[0], p[0], s[0]); // add on bit 0
add a1 (a[1], b[1], c_out, g[1], p[1], s[1]); // add on bit 1
// gp (g, p, c_in, g_out, p_out, c_out); // higher level g,p
gp gp0 (g, p, c_in, g_out, p_out, c_out); // higher level g,p
endmodule
module cla_4 (a,b,c_in,g_out,p_out,s); // 4-bit carry lookahead adder
input [3:0] a, b; // inputs: a, b
input c_in; // input: carry_in
output g_out, p_out; // outputs: g, p
output [3:0] s; // output: sum
wire [1:0] g, p; // internal wires
wire c_out; // internal wire
cla_2 a0 (a[1:0],b[1:0],c_in, g[0],p[0],s[1:0]); // add on bits 0,1
cla_2 a1 (a[3:2],b[3:2],c_out,g[1],p[1],s[3:2]); // add on bits 2,3
gp gp0 (g,p,c_in, g_out,p_out,c_out); // higher level g,p
endmodule
module cla_8 (a,b,c_in,g_out,p_out,s); // 8-bit carry lookahead adder
input [7:0] a, b; // inputs: a, b
input c_in; // input: carry_in
output g_out, p_out; // outputs: g, p
output [7:0] s; // output: sum
wire [1:0] g, p; // internal wires
wire c_out; // internal wire
cla_4 a0 (a[3:0],b[3:0],c_in, g[0],p[0],s[3:0]); // add on bits 0-3
cla_4 a1 (a[7:4],b[7:4],c_out,g[1],p[1],s[7:4]); // add on bits 4-7
gp gp0 (g,p,c_in, g_out,p_out,c_out); // higher level g,p
endmodule
module cla_16 (a,b,c_in,g_out,p_out,s); // 16-bit carry lookahead adder
input [15:0] a, b; // inputs: a, b
input c_in; // input: carry_in
output g_out, p_out; // outputs: g, p
output [15:0] s; // output: sum
wire [1:0] g, p; // internal wires
wire c_out; // internal wire
cla_8 a0 (a[7:0], b[7:0], c_in, g[0],p[0],s[7:0]); // add on bits 0-7
cla_8 a1 (a[15:8],b[15:8],c_out,g[1],p[1],s[15:8]); // add on bits 8-15
gp gp0 (g,p,c_in, g_out,p_out,c_out); // higher level g,p
endmodule
module CLA_32(a,b,c_in,g_out,p_out,s);
input [31:0] a, b; // inputs: a, b
input c_in; // input: carry_in
output g_out, p_out; // outputs: g, p
output [31:0] s; // output: sum
wire [1:0] g, p; // internal wires
wire c_out; // internal wire
cla_16 a0 (a[15:0], b[15:0], c_in, g[0],p[0],s[15:0]); // + bits 0-15
cla_16 a1 (a[31:16],b[31:16],c_out,g[1],p[1],s[31:16]); // + bits 16-31
gp gp0 (g,p,c_in,g_out,p_out,c_out);
endmodule
module cla32 (a,b,ci,s); // 32-bit carry lookahead adder, no g, p outputs
input [31:0] a, b; // inputs: a, b
input ci; // input: carry_in
output [31:0] s; // output: sum
wire g_out, p_out; // internal wires
CLA_32 cla (a, b, ci, g_out, p_out, s); // use cla_32 module
endmodule
Simulational Results:
Parametrized Version Verilog Code:
module carry_lookahead_adder(A,B,S,Cout,Cin);
parameter N = 4;
input [N-1:0]A,B;
input Cin;
output [N-1:0]S;
output Cout;
wire [N-1:0]P, G ;
wire [N:0]C;
propagate_generate #(.N(N)) M1(.A(A), .B(B), .P(P), .G(G));
carry_generate #(.N(N)) M2 (.P(P), .G(G), .C(C), .Cin(Cin));
assign S = P ^ C;
assign Cout = C[N];
endmodule
module propagate_generate(A,B,P,G);
parameter N = 4;
input [N-1 :0] A,B;
output [N-1 :0]P,G;
assign P = A^B;
assign G = A&B;
endmodule
module carry_generate(P,G,C,Cin);
parameter N = 4;
input [N-1:0]P,G;
input Cin;
output [N:0]C;
assign C[0] =Cin;
genvar i;
generate for(i=1;i<=N;i=i+1) begin
assign C[i] = G[i-1] | (P[i-1]&C[i-1]);
end
endgenerate
endmodule
Test Bench Verilog Code:
module tb;
reg [2:0]A,B;
wire [2:0]S;
reg Cin;
wire Cout;
carry_lookahead_adder #(.N(3)) DUT(.A(A), .B(B), .S(S), .Cout(Cout), .Cin(Cin));
task load(input [2:0]a,b, input c); begin
A = a;
B = b;
Cin = c;
end
endtask
integer i , j,k;
initial begin
$dumpfile ("carry_lookahead_adder.vcd");
$dumpvars (0, tb);
for (k=0;k<2;k=k+1) begin
for (i=0; i<8 ; i=i+1) begin
for(j=0;j<8;j=j+1) begin
load(i,j,k);
#10;
end
end
end
$finish;
end
initial $monitor("A = %b, B = %b, Cin = %b, Cout = %b, Sum = %b",A,B,Cin,Cout,S);
endmodule
Simulational Results:
If you want to implement its entire RTL to GDSII then refer to the below articles series.
Great post bro help me on miniproject.
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