module tq(
  input  [N-1:0] in,
  output [5:0]  out
);

parameter N = 53;

always_comb
  begin
    out = 4'b0000;
    for(int i = N-1; i>=0; i--)
      if(in[i])
        out = i;    
  end



endmodule

module m52_6(rst,clk,in_i,out_o,keyEv);

    input        rst, clk;
    input  [51:0] in_i;
    output [5:0]  out_o;
    output        keyEv;

reg [51:0] inReg;
reg [5:0]  keyCtr;

assign    keyEv = ~inReg[51];

always @ (posedge clk)
    if (rst)           inReg <= in_i;
    else begin
        if (keyEv)     inReg <= in_i;
        else           inReg[51:0] <= {inReg[51:0], inReg[51]}; end

always @ (posedge clk)
    if (rst)        keyCtr <= 0;
    else if(~keyEv) keyCtr <= keyCtr + 1;
    else            keyCtr <= 0;
    assign out_o = keyCtr;
    
endmodule