What happens if you take current_state out of the process sensitivity 
list? input should be the ony one because otherwise it will run in a 
endless loop.

> But it doesn't seem to work.
How do you see that?

Indeed there are several problems inside the code:

1

-- a little bit curious combinational and clocked process...   :-o    process(clock, reset)

2

begin

3

    -- a clocked part

4

    if (reset='1') then                       

5

        current_state <= 0;  

6

    elsif (clock'event and clock='1') then               

7

        current_state <= next_state;

8

    end if;

9

10

    -- and a combinational part

11

    if current_state = 8 then   -- current_state is missing in the sensitivity list!

12

        output <= '1';

13

    else

14

        output <= '0';

15

    end if;  

16

end process;

And this is, why the thing never will work reliably on hardware:

1

process(current_state,input)

2

begin

3

  case current_state is

4

      when 0 =>                            

5

         if input = "0000000001" then   -- input is not synchronized to clock!

Every asynchronous input MUST be synchronized to the internal clock by 2 
flipflops. Try this with google translator:
http://www.lothar-miller.de/s9y/categories/35-Einsynchronisieren
http://translate.google.de/translate?sl=de&tl=en&js=n&prev=_t&hl=de&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.lothar-miller.de%2Fs9y%2Fcategories%2F35-Einsynchronisieren&act=url
It gives a crude translation, but maybe you will get the idea...

I tried removing the input from the sensitivity list but it doesn't 
change the graph.
I know it doesn't work from the graph, when I test it.

Some questions:
What do I need to include in the sensitivity list?
All things I use in the processes, in my case current_state, next_state, 
input etc? This isn't the case in many examples.

I tried reading the article, however I can't grasp most of those terms 
and the translator isn't helping that much. Maybe I should use something 
like
"wait on clock until clock = '1'".

> What do I need to include in the sensitivity list?
Keep one thing in mind: the sensitivity list is ONLY for simulation.
The synthesizer ignores this list!

So the list must contain every signal that requires a calculation of the 
process in simulation. In the case of this one
    process(clock, reset)
the current_state is missing (due to the curious 
clocked-and-combinational style).
In this process
    process(current_state,input)
the list is complete. At a change of current_state or a change of 
input the process must be calculated.

> I tried reading the article, however I can't grasp most of those terms
> and the translator isn't helping that much.
Its a long way to go... :-(

> Maybe I should use something like "wait on clock until clock = '1'".
I prefer this:
   wait until rising_edge(clock);
And so ALL of my processes are concurrent, and i do not have a 
current_state and a next_state. I have just the state...

So my description would look like this:

1

    process begin

2

        wait until rising_edge(clock);

3

  case current_state is

4

      when 0 =>  if input = "0000000001" then 

5

         state <= 1;               

6

      end if;

7

8

      when 1 =>  if input = "0000000000" then 

9

         state <= 2;

10

      else          

11

         state<= 0;

12

      end if;

13

14

      when 2 =>  if input = "0000000001" then

15

         state <= 3;

16

      else          

17

         state < =0 ;

18

      end if;

19

20

      when 3 =>  if input = "0000001000" then 

21

         state <= 4;

22

      else          

23

         state <= 0;

24

      end if;

25

            :

26

            :

27

            :

28

29

      when 7 =>   if input = "0000001001" then 

30

         state <= 8;

31

      else          

32

         state <= 0;

33

      end if;

34

35

      when 8 =>   state <= 0;  

36

37

  end case;

38

    end process;

39

40

    output <= '1' when state=8 else '0';

One word to the when others

1

    signal next_state, current_state: integer range 0 to 8;

2

      :

3

      :

4

      when 8 =>          

5

      next_state <= 0;  

6

      when others =>                 -- ignored!

7

      next_state <= 0;

The states only can have the values 0 to 8. Thats the way they are 
defined! When you use all of these values explicitly the are no 
remainings for when others. These last path is simply ignored and 
therefore needless.

I modified my code, now it gives these errors.
The rising_edge line gives me this error:
Prefixed name 'rising_edge' is not a 1 dimensional array or a function 
or contains a bad suffix (index/slice/selected-name).

Also there is another error, the simulator fails to connect:
Unresolved signal 'state' has more than one source

I also tried with my old code, used the rising_edge function, but it too 
doesn't like it.

> Unresolved signal 'state' has more than one source
That says: you are driving the signal e.g. from more than 1 process or 
from a process and also concurrent...

> I modified my code, now it gives these errors.
Why did you add a process? With my code you have only ONE process. And 
this one is clocked. This design style is a little bit different to the 
"usual" style you can find in most ancient books. Try to search for a 
"one process fsm".

Get rid of this (its already in the FSM process) nd your design will 
run:

1

    process(clock, reset)

2

    begin

3

  if (reset='1') then                       

4

    state <= 0;  

5

  elsif (clock'event and clock='1') then               

6

    state <= state;                              

7

  end if;

8

    end process;

BTW: did you think a little of anything when you wrote that code? Wich 
every clock you assign state to state. What should this be good for?

> I also tried with my old code, used the rising_edge function, but it
> too doesn't like it.
You must not TRY, you must UNDERSTAND...

Thank you for your help.
I feel blindfolded when writing VHDL (the asynchronous stuff), I know? 
the syntax but the inner workings might go over my head.

The code was "compiled" from different examples(with modifications of 
course), so I did my best when knowing very little.
Usually I am an avid googler, but it seems that there is very little 
information about VHDL even forums are hard to find.

I still added this other process, because there is the reset ?variable, 
even though the state<=state is useless.

I removed the other process and it still gives me those errors.
Also, the rising_edge(clock) still gives me the same error. Perhaps it's 
a simulator specific thing.
It compiles with "wait on clock until clock = '1'",
but the graph doesn't show me anything. The reset variable is 1 in 
graph.

I want to understand.