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Altera_Forum
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15 years ago

multiplication in fixed_pkg

sir/mam i am using fixed_pkg_c.vhdl for multiply 0.46 with a wc which is std_logic_vector of 14 bits.i represent 0.46 using sfixed command,but can't understand how to convert std_logic_vector t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

to convert std_logic_Vector there is a function called 


function to_sfixed (     
arg                  : STD_ULOGIC_VECTOR;  -- shifted vector     
constant left_index  : INTEGER; 
    constant right_index : INTEGER)     
return UNRESOLVED_sfixed;

or there is this version: 


function to_sfixed (     
arg      : STD_ULOGIC_VECTOR;       -- shifted vector     size_res : UNRESOLVED_sfixed)       -- for size only     return UNRESOLVED_sfixed;

where you can use another signal for sizing information

so for example, to convert a 14 bit slv to an sfixed with 6 integer bits and 8 fractional, use the function like this:

output <= to_sfixed(my_slv, 5, -8);

or you can do this:

output <= to_sfixed(my_slv, output);