shaiko
Advanced Member level 5
I wrote a restoring division function and tried to test it with modelsim.
Signals a,b,c are defined as follows:
I run the simulation in 2 different ways:
The error message from modelsim:
The function description:
Signals a,b,c are defined as follows:
Code:
signal a : unsigned ( 3 downto 0 ) := "1000" ;
signal b : unsigned ( 1 downto 0 ) := "10" ;
signal c : unsigned ( 3 downto 0 ) ;I run the simulation in 2 different ways:
Code:
c <= restoring_divide ( a , b ) ; -- works proparly ( c gets "0100" )
Code:
c <= restoring_divide ( "1000" , "10" ) ; -- failsThe error message from modelsim:
The function description:
Code:
function restoring_divide
(
numerator : unsigned ;
denominator : unsigned
)
return unsigned is
variable temp_numerator : unsigned ( numerator ' range ) := numerator ;
variable temp_numerator_with_denominator_length : unsigned ( denominator ' range ) := ( others => '0' ) ;
variable temp_denominator : unsigned ( denominator ' range ) := denominator ;
variable temp_denominator_with_numerator_length : unsigned ( numerator ' range ) := ( others => '0' ) ;
variable temp_remainder : unsigned ( denominator ' length downto 0 ) := ( others => '0' ) ;
variable temp_remainder_with_numerator_length : unsigned ( numerator ' length downto 0 ) := ( others => '0' ) ;
begin
if numerator ' length = denominator ' length then
for index in 0 to denominator ' length - 1
loop
temp_remainder ( denominator ' length - 1 downto 1 ) := temp_remainder ( denominator ' length - 2 downto 0 ) ;
temp_remainder ( 0 ) := temp_numerator ( numerator ' length - 1 ) ;
temp_numerator ( numerator ' length - 1 downto 1 ) := temp_numerator ( numerator ' length - 2 downto 0 ) ;
temp_remainder := temp_remainder - temp_denominator ;
if ( temp_remainder ( denominator ' length ) = '1' ) then
temp_numerator ( 0 ) := '0' ;
temp_remainder := temp_remainder + temp_denominator ;
else
temp_numerator ( 0 ) := '1' ;
end if ;
end loop ;
return temp_numerator ;
elsif numerator ' length > denominator ' length then
temp_denominator_with_numerator_length := resize ( denominator , numerator ' length ) ;
for index in 0 to temp_denominator_with_numerator_length ' length - 1
loop
temp_remainder_with_numerator_length ( temp_denominator_with_numerator_length ' length - 1 downto 1 ) :=
temp_remainder_with_numerator_length ( temp_denominator_with_numerator_length ' length - 2 downto 0 ) ;
temp_remainder_with_numerator_length ( 0 ) := temp_numerator ( numerator ' length - 1 ) ;
temp_numerator ( numerator ' length - 1 downto 1 ) := temp_numerator ( numerator ' length - 2 downto 0 ) ;
temp_remainder_with_numerator_length := temp_remainder_with_numerator_length - temp_denominator ;
if ( temp_remainder_with_numerator_length ( temp_denominator_with_numerator_length ' length ) = '1' ) then
temp_numerator ( 0 ) := '0' ;
temp_remainder_with_numerator_length := temp_remainder_with_numerator_length + temp_denominator ;
else
temp_numerator ( 0 ) := '1' ;
end if ;
end loop ;
return temp_numerator ;
else
temp_numerator_with_denominator_length := resize ( numerator , denominator ' length ) ;
for index in 0 to denominator ' length - 1
loop
temp_remainder ( denominator ' length - 1 downto 1 ) := temp_remainder ( denominator ' length - 2 downto 0 ) ;
temp_remainder ( 0 ) := temp_numerator_with_denominator_length ( temp_numerator_with_denominator_length ' length - 1 ) ;
temp_numerator_with_denominator_length ( temp_numerator_with_denominator_length ' length - 1 downto 1 ) :=
temp_numerator_with_denominator_length ( temp_numerator_with_denominator_length ' length - 2 downto 0 ) ;
temp_remainder := temp_remainder - temp_denominator ;
if ( temp_remainder ( denominator ' length ) = '1' ) then
temp_numerator_with_denominator_length ( 0 ) := '0' ;
temp_remainder := temp_remainder + temp_denominator ;
else
temp_numerator_with_denominator_length ( 0 ) := '1' ;
end if ;
end loop ;
return temp_numerator_with_denominator_length ;
end if ;
end function restoring_divide ;
Last edited: