Comments on Priority Example
This is the first example that used a bus. The DOUT signal is a 3 bit output bus.
- std_logic_vector(2 downto 0) describes a 3 bit bus where dout(2) is most significant bit, dout(0) is least significant bit.
- std_logic_vector (0 to 2) is also a 3 bit bus, but dout(0) is MSB, dout(2) is LSB. We will always use 'downto' in this class.
A bus assignment can be done in many ways:
- dout <= "110"; assigns all three bits
- dout(2) <= '1'; assigns only bit #2
- dout(1 downto 0) <= "10"; assigns two bits of the bus.
This architecture used the 'elsif' form of the 'if' statement
- Note that it is 'elsif', NOT 'elseif'.
- This called an elsif chain.