calculate 64 bit unsigned

function get_phase_inc(Fout,clk,N : natural) return std_logic_vector is 
variable phase : integer;
begin
  phase := Fout*2**N/clk;
  return std_logic_vector(to_unsigned(phase,N));
end function;
signal test : std_logic_vector(7 downto 0);
...
test <= get_phase_inc(10,100,8);

the problem arises when N is 64 as a integer is not enough to represent it.

function phase_inc(Fout,clk, N : natural) return std_logic_vector is 
variable phase : integer;
variable temp1,temp2:unsigned(N/2-1 downto 0);
begin
  phase := Fout*(2**N/2)/clk;
  temp1 := to_unsigned(phase,32);
  phase := (2**N/2)/clk;
  temp2 := to_unsigned(phase,32);
  return std_logic_vector(temp1*temp2);
end function;

actually you need to go lower than 2^32 as temp1,temp2 exceed 2^32, try 2^16

I finally see no way to get value without losing resolution as there is no support for 64 bits range

looks like this will work (not a function)

constant fo:unsigned(31 downto 0) := x"11110000";
constant fclk : unsigned(31 downto 0) := x"ffff0000";
constant temp: unsigned(95 downto 0) := fo & x"0000000000000000";
constant phase : unsigned(95 downto 0) := temp/fclk;

ok I'll try this way then I'll let you know...

It works thanks