I keep getting an error when I simulate the CLA4Top, CLA8Top and the test. The testbench was given and the entire project compiles. For the CLA4Top I thought it looked like "cout" is coming out to be correct but "sum" is not matching the expected outputs. I changed that and this is the updated code:
Here is the CLA4Top.sv
//4 bit carry lookahead adder
module CLA4Top(ain, bin, cin, sum, cout);
//parameter nBITS = 4;
//logic [nBITS - 1 : 0] ain, bin, sum;
//logic cin, cout;
input [3:0] ain, bin;
input cin;
output logic [3:0] sum;
output logic cout;
CLA4Bit C1(.*);
test #(4) TB(.*);
endmodule
module CLA4Bit (ain, bin, cin, sum, cout);
timeunit 1ns/1ns;
input [3:0] ain, bin;
input cin;
output logic [3:0] sum;
output logic cout;
wire p0,p1,p2,p3,g0,g1,g2,g3,c1,c2,c3,c4,c0;
assign p0=(ain[0]^bin[0]),
p1=(ain[1]^bin[1]),
p2=(ain[2]^bin[2]),
p3=(ain[3]^bin[3]);
assign g0=(ain[0]&bin[0]),
g1=(ain[1]&bin[1]),
g2=(ain[2]&bin[2]),
g3=(ain[3]&bin[3]);
assign c0=cin,
c1=g0|(p0&cin),
c2=g1|(p1&g0)|(p1&p0&cin),
c3=g2|(p2&g1)|(p2&p1&g0)|(p1&p1&p0&cin),
c4=g3|(p3&g2)|(p3&p2&g1)|(p3&p2&p1&g0)|(p3&p2&p1&p0&cin);
assign sum[0] = ain[0] ^ bin[0] ^ cin,
sum[1] = ain[1] ^ bin[1] ^ c1,
sum[2] = ain[2] ^ bin[2] ^ c2,
sum[3] = ain[3] ^ bin[3] ^ c3;
assign cout=c4;
endmodule
Here is the CLA8Top.sv
// module with 8 bit adder using 4 bit CLA instances
module CLA8Top(ain, bin, cin, sum, cout);
//parameter nBITS = 8;
input [7:0] ain, bin;
input cin;
output logic [7:0] sum;
output logic cout;
wire c1;
// CLA4Bit c11(ain[3:0],bin[3:0],1'b0,sum[3:0],c1);
CLA4Bit c11(ain[3:0],bin[3:0],cin,sum[3:0],c1);
CLA4Bit c22(ain[7:4],bin[7:4],c1,sum[7:4],cout);
test #(8) TB(.*);
endmodule
And this is the testbench.sv
// Test bench for Generic N-Bits Adder design module
module test(ain, bin, cin, sum, cout);
timeunit 1ns/1ns;
parameter nBITS = 4;
parameter DELAY = 100;
input [nBITS - 1 : 0] sum;
input cout;
output [nBITS - 1 : 0] ain, bin;
output cin;
logic [nBITS - 1 : 0] ain, bin, sum;
logic cin, cout;
// test variables
logic [nBITS : 0] exp_value;
int i, j, test_count;
bit error;
initial begin
error = 0;
test_count = 0;
cin = 0;
repeat(2) begin
for(i = 0; i < (1 << nBITS); i++) begin
ain = i;
for(j = 0; j < (1 << nBITS); j++) begin
test_count++;
bin = j;
exp_value = ain + bin + cin;
#DELAY;
if({cout, sum} !== exp_value) begin
$display("For inputs: ain = %b, bin = %b, cin = %b :: Actual outputs: cout = %1b, sum = %b :: Expected outputs: cout = %1b, sum = %b", ain, bin, cin, cout, sum, exp_value[nBITS], exp_value[nBITS-1:0]);
error = 1;
end // end for if block
end // end for j for loop
end // end for i for loop
cin = ~cin;
end // end for repeat block
if(error === 0)
$display("***Congratulations, No errors found after %d tests***", test_count);
else
$display("***Sorry, errors found in your code ***");
end // end for initial block
endmodule
Is there any changes that I can make that would give me the $display("***Congratulations, No errors found after %d tests***", test_count); that you can see? What problems am I having and why? I will include the transcript from running the CLA4Top.sv.
