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6. Sequential Logic
„I Know What You Did Last Cycle“
6.1 State Diagram, State Transition Diagram
6.1.1 Motivation
The diagrams of different states are well known from physics for example the state diagram (or better: phase diagram) of water, where its three states are: solid ice, liquid water and gaseous steam. The possible state transitions are due to temperature increase or decrease.
In Abbildung 9 image (1) the states of water are shown on the temperature axis. When only the state transistions are relevant, the states are simplified to a circle, showing the state name and behaviour. The transitions are depict as arrows, where the needed condititon is written onto (See Abbildung 9 image (2) ). This diagram is called state transition diagram.
For matter not only the dimension „temperature“ is important, but also the „pressure“. The full phase diagram is shown in Abbildung 10 image (1). By this, another variable is available and more transistions. These can be drawn into the state transition diagram (Abbildung 10 image (2)).
6.1.2 Simple logic Example
In German, often one has to pay for entering the toilet. An example of such a entrance control system is shown in Abbildung 11. At this (artificial) example, one can pay either 50ct or 1€.
Once paid, the turnstile will release and one can enter. Once the turnstile was pushed the entrance is closed again.
The Abbildung 12 the state transition diagram is drawn.
- The two states are that (1) the turnstile is opened and one is able to go through and (2) the turnstile is closed and one cannot enter anymore.
- The transitions are given by the done actions: one can either insert a coin or push on the turnstile.
Out of this state transition diagram one can create a table-like representation, see Abbildung 13.
