Question

i am beginner in VHDL and i need do login terminal. For example i have fixed password 7010. I need implement only funcionality of automat. I want to have defined one signal, that will hold count of keys presses and will be incremented each time.

But i dont know how to initialize signal and incerement it, because when i initialize signal in one process, i cant increment its value in other process. If i dont intialize that signal, then my code not work and i dont know why. For example doSomething will not be runned if i dont that signal to “0000”. But i need incerement its value in doSomething… Sry for my bad english.

if(mySignal = "0000")
    doSomething

Answer 1

What you are trying to do sounds like a class assignment.

Break the problem down.

Draw a block diagram of what you want

In synthisisable VHDL you are correct in saying, unless the signal can be high Z, multiple drivers are not allowed.
But there is nothing to stop you taking a copy of the signal and using that in another process.

Make use of unsigned types for counters or any signal that has magnitude, it makes life much easier

doSomething:process(clk,mySignal
begin
    if rising_Edge(clk) then
        if mySignal = "0000" then
            count<=count+1;
        end if;
    end if;
end process;