VHDL issues

i'm making a cache for my VHDL class. problem is i'm a moron and apparently don't understand VHDL at all. so there is

    tag_ram: entity    work.tag_RAM(behav)
        port map(address => Paddress(9 downto 2),
            WRITE_ACTIVE_HIGH => NOTPRW,
            ENABLE => TAGENABLE,
            new_tag => Paddress(15 downto 10),
            tag => TAGDATAOUT);

but the only important part of this is that when TAGENABLE is high then TAGDATAOUT is supposed to end up with some value set to it, it does so through this piece of code:


    main : process(address, WRITE_ACTIVE_HIGH, ENABLE, new_tag) is
    begin
        if (WRITE_ACTIVE_HIGH = '0' and ENABLE = '1') --read
        then
            tag <= MEM(to_integer(address)) after 1 ns;
        end if;
        if (WRITE_ACTIVE_HIGH = '1' and ENABLE = '1') --write
        then
            MEM(to_integer(address)) <= new_tag after 1 ns;
        end if;
    end process main;


which for some reason never seems to figure out that TAGENABLE got set to one.  i have report statements in the real version of the code that basically suggest this code gets "stuck" before it can figure out that TAGENABLE went to one. if anyone knows enough about VHDL to guide me i'd be grateful.

>>22

fair enough. as for the explanation, it is a cache that is starting out empty, so the first few times it accessess data there's nothing in the cache. if you put any value, even all 0s in you run the risk of mistaking it for an actual value.

However i worked around that particular problem by not waiting for activity on that signal and waiting on something else instead.

meanwhile, i am now having trouble with inout signals, for some reason if i have even only one process driving an inout signal it always comes out "U" but i can circumvent this issue by changing it to an in or out respectively (which hasn't cause funcitonal issues yet because the assignment only required us to do system reads, not system writes).

Can the other VHDL person on here explain inout to me? like special precautions i have to take in order to work with it?