DE2 board USB communication

i changed, but an new Error is appear...

count := count + 1;

case count is

when 0 => NULL;

when 1 => word_buffer (03 downto 00) <= in_data;

when 2 => word_buffer (07 downto 04) <= in_data;

when 3 => word_buffer (11 downto 08) <= in_data;

when 4 => word_buffer (15 downto 12) <= in_data;

buffer_full <= '1';

bufferpicked: if tmp = '0' then buffer_picked <= '0';

elsif tmp = '1' then buffer_picked <= '1'; end if;

Error : slice that is assigned to target slice has 16 elements, but must have same number of element as target slice (4) Error: Can’t elaborate top-level user hierarchy