A state machine is a theoretical construct utilized to depict the behavior of a system, which can include software applications, electronic devices, or any other category of systems. This framework includes various states, each denoting a distinct condition or mode of operation, as well as transitions that govern the behavior of the system. State machines are integral to the design and execution of software systems, particularly within embedded systems. They assist in handling complex logic and controlling system behavior in reaction to diverse events and inputs. A variety of programming languages and tools can be employed for state machine implementation, and they are commonly applied in real-time systems, control systems, and the development of user interfaces.
A Finite State Machine (FSM) It is a particular kind of state machine characterized by a limited number of states and the transitions that occur between them. Within a finite state machine (FSM), the system is confined to a specific set of states, and the changes between these states occur as a result of certain events or inputs. FSMs are essential in the design and implementation of hardware systems, including digital circuits and microcontrollers. They are also prominently used in software systems, especially in areas like natural language processing and game development.
Mealy Machine
The output of a Mealy machine is influenced by the current state as well as the input it processes, as soon as a transition takes place, the output is created. The state transition table contains input and output values, which means that output is generated as the machine progresses from one state to the next. This category of state machine is beneficial in scenarios where the output is influenced by both the present input and the existing state. For instance, a vending machine reveals the product information as soon as the user picks a certain item.
Moore Machine
The output of a Moore machine is influenced exclusively by its current state, rather than by any input. The generation of output occurs only when the machine reaches a new state, and does not take place during the transition phase. Only input values are represented in the state transition table, while the output corresponds to each individual state. This variant of state machine is effective in contexts where the output is contingent only upon the existing state. A pertinent example is a traffic light system that modifies its color depending on the existing situation.
Hierarchical State Machine
Multiple state machines form hierarchical state machines, with each machine acting as a subsystem or module that contributes to the overall system. Every subsystem features a specific arrangement of states and transitions, and it is capable of having its own sub-state machines. This form of state machine is advantageous for modeling sophisticated systems that can be segmented into more manageable subsystems. Consider the airplane control system as an example, where each subsystem, like the engine, navigation, and landing gear, is characterized by its own specific states and transitions.
Harel State chart
A Harel state chart is a form of hierarchical state machine that integrates the principle of concurrency. This approach is utilized to simulate systems that involve several parallel processes or events occurring simultaneously. Within a Harel statechart, it is possible for a state to include various concurrent sub-states, each of which can have a separate collection of transitions and events. This variant of state machine proves beneficial in the representation of complex systems that feature various parallel processes or events, especially in real-time control system applications.
Control logic:
Many embedded systems employ a state machine to model their control logic effectively. The control logic serves to regulate the power modes of the system, address interrupts, and carry out various other vital system operations. State machines can serve as a mechanism for overseeing the power management of battery-driven devices, like mobile phones and smart watches. By adjusting its power modes in response to the device’s activity and battery levels, the state machine effectively controls the power consumption of the device.
User interface:
In embedded systems, another typical application of state machines is to simulate the user interface. The user interface can be conceptualized as a state machine, where various states correspond to distinct screens, menus, or operational modes. In the context of a digital thermometer, a state machine can be employed to regulate its display, with distinct states denoting various temperature ranges and the transitions illustrating the fluctuations in temperature.
Sensor data acquisition:
State machines are commonly employed in various embedded systems to collect and analyze data from sensors. By utilizing a state machine allows for effective control over the data acquisition process, ensuring that the data is processed and stored correctly. A state machine can facilitate the acquisition and processing of data from a temperature sensor, where each state corresponds to various phases of the data acquisition process, including data collection, filtering, and storage.