//
// System reset test.
//
// This is not yet self-verifying code.
// (Which means you have to look at the waveform)
//

// 
// 
// Design by G.J. van Loo, FenLogic Ltd, 15-January-2017.
// 
// This program is free software. It comes without any guarantees or
// warranty to the extent permitted by applicable law. Although the
// author has attempted to find and correct any bugs in this free software
// program, the author is not responsible for any damage or losses of any
// kind caused by the use or misuse of the program. You can redistribute
// the program and or modify it in any form without obligations, but the
// author would appreciated if the credits stays in.
// 

module system_reset_test; 

localparam XTAL_PERIOD = 80;


reg   xtal;
reg   xtal_on;
wire  xtal_ok;
reg   reset_n_raw;
wire  sys_reset_n;

initial
begin
   reset_n_raw = 1'b0;
   xtal_on     = 1'b0;
   #100;
   reset_n_raw = 1'b1;
   #(50*XTAL_PERIOD) ;
   @(negedge xtal)
      xtal_on = 1'b1;
   
   wait (sys_reset_n == 1'b1)
   #(70*XTAL_PERIOD) ;
   $stop;
end

// Clean XTAL signal
initial
begin
   xtal= 1'b0;
   forever
      #(XTAL_PERIOD/2) xtal<= ~xtal;
end

assign xtal_ok = xtal & xtal_on;

system_reset system_reset_0
   (
   .xtal_ok    (xtal_ok    ), // signal from crystal oscillator pad
   .reset_n_raw(reset_n_raw), // signal direct from reset-pad
   .sys_reset_n(sys_reset_n) // reset to be distributed
   );

endmodule // system_reset_test