Q. Write Code for Pattern Detector 10110. Input to DUT is 1 bit and output is 1 bit.
How can I implement without queue?
If I change queue to array in below code I get flag=1 twice. Why?
EDA Link: EDA Playground
Design.sv
module pattern_detect(input clk, input rst, input bit in, output flag);
logic pat_seq[\$]='{1,0,1,1,0};
logic pat_in[\$]='{0,0,0,0,0};
reg flag=0;
always @(posedge clk) begin
if(!rst) begin
pat_in.pop_front();
pat_in.push_back(in);
//Issue with using array
// pat_in[4]<=pat_in[3];
// pat_in[3]<=pat_in[2];
// pat_in[2]<=pat_in[1];
// pat_in[1]<=pat_in[0];
// pat_in[0]<=in;
if(pat_in == pat_seq) begin
flag <= 1;
$display(" *************************** ");
$display("flag is 1 @time=%0d", $time);
$display(" *************************** ");
foreach(pat_in[i]) begin
$display("pat_in[%0d]=%0d", i, pat_in[i]);
end
$display("***************************");
end
else begin
flag <= 0;
$display("flag is 0 @time=%0d", $time);
foreach(pat_in[i]) begin
$display("pat_in[%0d]=%0d", i, pat_in[i]);
end
end
end
if(rst)
flag <=0 ;
end
endmodule
**[u]Testbench.sv[/u]**
module test;
reg clk=0;
reg rst=1;
reg in=0;
wire flag;
pattern_detect pat(.clk(clk), .rst(rst), .in(in), .flag(flag));
initial begin
forever begin
#10 clk = ~clk;
end
end
initial begin
// Dump waves
$dumpfile("dump.vcd");
$dumpvars(1, test);
#10 rst=0;
in=0;
#20 in=1;
#20 in=1;
#20 in=0;
#20 in=1;
#20 in=1;
#20 in=0;
#20 in=1;
#20 in=0;
#20 in=0;
#20 in=1;
#20 in=0;
#20 in=1;
$finish;
end
endmodule
Log
flag is 0 @time=10
pat_in[0]=0
pat_in[1]=0
pat_in[2]=0
pat_in[3]=0
pat_in[4]=0
flag is 0 @time=30
pat_in[0]=0
pat_in[1]=0
pat_in[2]=0
pat_in[3]=0
pat_in[4]=1
flag is 0 @time=50
pat_in[0]=0
pat_in[1]=0
pat_in[2]=0
pat_in[3]=1
pat_in[4]=1
flag is 0 @time=70
pat_in[0]=0
pat_in[1]=0
pat_in[2]=1
pat_in[3]=1
pat_in[4]=0
flag is 0 @time=90
pat_in[0]=0
pat_in[1]=1
pat_in[2]=1
pat_in[3]=0
pat_in[4]=1
flag is 0 @time=110
pat_in[0]=1
pat_in[1]=1
pat_in[2]=0
pat_in[3]=1
pat_in[4]=1
flag is 1 @time=130
pat_in[0]=1
pat_in[1]=0
pat_in[2]=1
pat_in[3]=1
pat_in[4]=0
flag is 0 @time=150
pat_in[0]=0
pat_in[1]=1
pat_in[2]=1
pat_in[3]=0
pat_in[4]=1
flag is 0 @time=170
pat_in[0]=1
pat_in[1]=1
pat_in[2]=0
pat_in[3]=1
pat_in[4]=0
flag is 0 @time=190
pat_in[0]=1
pat_in[1]=0
pat_in[2]=1
pat_in[3]=0
pat_in[4]=0
flag is 0 @time=210
pat_in[0]=0
pat_in[1]=1
pat_in[2]=0
pat_in[3]=0
pat_in[4]=1
flag is 0 @time=230
pat_in[0]=1
pat_in[1]=0
pat_in[2]=0
pat_in[3]=1
pat_in[4]=0
$finish called from file “testbench.sv”, line 50.
Waveform
