counter, debouncer, parity

cntr.v

+module cntr(
+  input clk, rst, en, par,
+  output [3:0] q,
+);
+
+reg [3:0] cntr;
+
+always @ (posedge clk) begin
+  if(rst) begin
+    cntr <= 0;
+  end
+
+  else if(en) begin
+
+    if(par) begin
+      if(cntr >= 9) begin
+        cntr <= 0;
+      end
+      else begin
+        cntr <= cntr + 1;
+      end
+    end
+
+    else begin
+      if(cntr >= 8) begin
+        cntr <= 0;
+      end
+      else begin
+        cntr <= cntr + 1;
+      end
+    end
+
+  end
+end
+
+assign q = cntr;
+endmodule

debouncer.v

+module debouncer(
+input clk, rst, din,
+output q,
+);
+
+reg state;
+
+always @ (posedge clk) begin
+  if(rst) begin
+    state <= 0;
+  end
+
+  else begin
+    if(din) begin
+      state <= 1;
+    end
+    else begin
+      state <= 0;
+    end
+  end
+
+end
+
+assign q = (~state && din)
+endmodule

parity.v

+module parity(
+  input clk, rst, din,
+  output q,
+);
+
+reg t;
+
+always @ (posedge clk) begin
+  if(rst) begin
+//  t <= 0; // Even parity
+    t <= 1; // Odd parity
+  end
+
+  else if(din) begin
+    t <= ~t;
+  end
+end
+
+assign q = t;
+
+endmodule