module V_d_ff(q, qbar, clk, d);
 input clk,d;
 output q,qbar;
 voltage q, qbar, clk, d;
 parameter real tdelay   = 5n from [0:inf),
                ttransit = 5n from [0:inf),
                vout_high = 5,
                vout_low  = 0 from (-inf:vout_high),
                vth       = 1.4;

 integer x;
 analog
 begin
   @(initial_step) x = 0;

   @(cross(V(clk) - vth, +1 )) x = (V(d) > vth);

   V(q)    <+ transition( vout_high*x  + vout_low*!x, tdelay, ttransit );
   V(qbar) <+ transition( vout_high*!x + vout_low*x,  tdelay, ttransit );
 end
endmodule