Finite State Machines (FSM) Models


Examples include:
· Telephone with states – idle, receiving a ring, dialing, connected
· Washing Machine with states – washing, rinsing, drying
· Timers with states- idle, start, running
1) Inputs to the process changes the state to a new state. The process change from one state to another state is called as transition
2) A state can receive multiple tokens (inputs, messages, interrupt flags, semaphores, etc). A token means either an input or event input.
3) Event input is asynchronous, Eg. Semaphore taken or released, completion of execution of set of codes.
4) A state can similarly generate multiple tokens.



FSM for a Timer

FSM of an Interrupt Service Routine
There are 5 states namely – Idle, Call, running, blocked, return


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