Finite state machines and their applications in software for industrial control

Finite state machines (FSMs) are a common presence in digital circuit design. However, they can be very useful also for the software developer. Actual operating systems and application software are event-based and communication issues play a big role; these fields can be more easily handled with software based on finite state machines - software that is simpler and easier to understand, debug and modify. Embedded systems' software can also benefit from state machines because of their efficient way of using the limited resources of the system. The paper presents some basic concepts of finite state machines, some typical applications, with focus on Web technologies (modem control, FTP - File Transfer Protocol, remote access via Telnet console) and some implementation issues - programming finite state machines in Delphi for Windows, in microcontroller assembly language and C. Latest trends are also analyzed - the hardware implementation of state machines in silicon, like the new Texas Instruments MSP430 series of low power microcontrollers. These electronic packages offer some features like reduced power consumption, a single chip solution for complex applications and high functional flexibility.