initial

chapter2/calculator.v

@@ -0,0 +1,45 @@
+module calculator (
+  input [1:0] op,
+  input clk,
+  input rst,
+  output reg [31:0] Y
+);
+
+reg [31:0] A;
+reg [31:0] B;
+
+wire [5:0] B_rand;
+wire [3:0] A_rand;
+
+reg [31:0] Y_prev;
+
+assign A = {{28{1'b0}}, A_rand[5:0]};
+assign B = {{26{1'b0}}, B_rand[3:0]};
+
+always @(*) begin
+  if(!rst) begin
+    case(op)
+      2'b00 :Y =  A + B;
+      2'b01 :Y =  A - B;
+      2'b10 :Y =  A * B;
+      2'b11 :Y =  A / B;
+      default: Y = 0;
+    endcase
+  end 
+  else begin 
+    Y = 0;
+  end
+end
+
+always @(posedge clk) begin
+  if (rst) begin 
+    Y_prev <= 32'd0;
+    A <= 32'd0;
+    B <= 32'd0;
+  end 
+  else begin 
+    Y_prev <= Y;
+    A <= Y_prev;
+  end
+end
+endmodule