localparam Fclk = 50_000_000;//Hz
localparam Freq = 300_000;//Hz

localparam Fbase = (Freq/Fclk) * 2^32;
localparam Fstep =  Fbase / 128;

/// BITS_STREAM - Si5338 CLK = 320 kHz * 16 bit; When '1' - Freq data, when '0' Freq = Fbase;

assign phase_inc =  data_tx[8] ? Fbase + (data_tx[6:0] * Fstep):  Fbase - (data_tx[6:0] * Fstep );

///

always_comb begin
    if(data_tx[9])
        phase_mod = Fbase;
    else if (BITS_STREAM) begin
        phase_mod = phase_inc;
    end
    else
        phase_mod = Fbase;
end

///


nco_n U1(
    .phi_inc_i        (phase_mod),
    .clk                (DCLK),
    .reset_n            (1),
    .clken            (1),
    .phase_mod_i    (),
    .freq_mod_i        (),
    .fsin_o            (sin),
    .fcos_o            (cos),
    .out_valid        ()
);