module tb_top ();

    logic clk;
    logic nreset;

    clkgen clkgen_inst (
        .clk_o   (clk),
        .nreset_o(nreset)
    );

    gb gb_inst (
        .clk_i   (clk),
        .nreset_i(nreset)
    );

    // Testbench code
    logic        instr_undef;
    logic [15:0] last_pc;
    logic [ 7:0] last_opcode;

    assign instr_undef = gb_inst.cpu_inst.control_inst.is_undef;
    assign last_pc     = gb_inst.cpu_inst.control_inst.instr_pc_r;
    assign last_opcode = gb_inst.cpu_inst.control_inst.instr_r;

    always @(posedge clk) begin
        if (nreset && instr_undef) begin
            $info($sformatf("[%t] %X: Undefined opcode %X", $time(), last_pc, last_opcode));
            $fatal(0);
        end
    end

endmodule : tb_top