Using MOD doubles number of LEs in VHDL

hi

I'm just learning to programme an Altera MaxII development board having an EPM1270F256C5 CPLD.

I was able to send VGA signals to my monitor based on a 3-horizontal-stripes VHDL programme I found on the internet. I amended this to produce vertical stripes of width 32 pixels, on a 640x480 screen. I'm using just one colour for each red,green and blue. I did this in the 'case' statement by specifying the stripe pixel count for eaach stripe. The number of LE's used was 70.

architecture main of stripes_gen is

begin

process(vidon,hc)

variable hc_offset : std_logic_vector (9 downto 0):=(others=>'0');

variable div32 : std_logic_vector (9 downto 0):=(others=>'0');

variable int32 : integer;

variable rgb_s : integer;

begin

rgb<="000"; -- defined as an input std_logic_vector (2 downto 0), used for colours "red green blue"

hc_offset:=hc - 144; -- hc is the total horizontal pixel counter 0<=hc<800, hc_offset is the display horizontal counter, 0<=hc_offset<640

div32:="00000" & hc_offset(9 downto 5); -- divides hc_offset by 32 , 0<=div32<20, each one 32 pixels wide

int32:=conv_integer(div32); -- converts div32 to an integer , range from 0->19

if vidon = '1' then -- vidon=1 when hc is greater or equal to 144

case int32 is

when 0|3|6|9|12|15|18 =>

rgb(2)<='1';

when 1|4|7|10|13|16|19 =>

rgb(1)<='1';

when 2|5|8|11|14|17 =>

rgb(0)<='1';

when others =>

rgb<="111";

end case;

end if;

..

..

I wanted to make the code more 'efficient' by using MOD to create the 3 colours, without having to specify each stripe's starting pixel value, as above. The code below works, but the number of LEs used has shot up from 70 to 149, and I get lots of .tdf files generated, which I didn't before, such as lpm_divide_jql.tdf, sign_div_unsign_1nh.tdf, alt_u_div_tne.tdf and 7 variations on add_sub_e7c(f7c,g7c,h7c,h7c,i7c,m7c and u7c).tdf

The slightly changed MOD code is :-

..

..

hc_offset:=hc - 144;

div32:="00000" & hc_offset(9 downto 5); -- divides hc_offset by 32 to get a stripe 32 pixels wide

int32:=conv_integer(div32); -- converts div32 to an integer for easier dividing

rgb_s:=int32 mod 3 ; -- integer, gives either 0,1 or 2

if vidon = '1' then

case rgb_s is

when 0 =>

rgb(2)<='1';

when 1 =>

rgb(1)<='1';

when 2 =>

rgb(0)<='1';

when others =>

rgb<="111";

end case;

end if;

I thought this MOD code would have less overhead than the other, but it seems to be the opposite. What am I doing wrong.

regards