Problem with 7 segment display

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the only answer that i want (if is possible) is that:

i can insert into a vector an integer number in two different position? for example number 31 ---> 1 into index 0 and 3 into index 1

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Try this:

signal bcd : std_logic_vector(7 downto 0) := X"31";
signal hex_a_data : std_logic_vector(3 downto 0);
signal hex_b_data : std_logic_vector(3 downto 0);
-- Split the BCD value into two 4-bit values
hex_a_data <= bcd(3 downto 0);
hex_b_data <= bcd(7 downto 4);

Cheers,

Dave