1. 4 Bit Counter
PRBS Generator
Accumulator

2. 4 Bit counter
module count(Clock, Clear, out);
input Clock, Clear;
output [3:0] out;
reg [3:0]out;
always@(posedge Clock, negedge Clear)
if((~Clear) || (out>=16))out=4'b 0000;
else out=out+1;
endmodule
module Stimulus_v;
reg Clock;
reg Clear;
wire [3:0] out;
Count2Bit uut (
.Clock(Clock),
.Clear(Clear),
.out(out)
);
initial
begin
$display("ttt 4 Bit Counter");
$display("tt----------------------------------------");
$display("ttClockttClearttOutput[4]");
$display("tt----------------------------------------");
$monitor("tt %btt %b tt %b ",Clock,Clear,out);
#28 $display("tt----------------------------------------");
end
always
#1 Clock=~Clock;
initial
begin
Clock=0;Clear=0;
#10 Clear=1;
#16Clear=0;
#2 $stop;
end
endmodule

3. PRBS Generator
module prbsgen(clk, reset, en, q);
input clk, reset, en;
output [7:0] q;
reg [7:0] q;
always @(posedge clk or posedge reset)
begin
if (reset)
q <= 8'd 1;
else if (en)
q <= {q[6:0], q[7] ^ q[5] ^ q[4] ^ q[3]};
end
endmodule
Accumulator
module accumlator(Clk, CLR, D, Q);
input Clk, CLR;
input [3:0] D;
output [7:0] Q;
reg [7:0] tmp;
always @(posedge Clk or posedge CLR)
begin
if (CLR)
tmp = 4'b0000;
else
tmp = tmp + D;
end
assign Q = tmp;
endmodule