Andy:

(every project should have one).

I have one medical product I worked on that uses the 68HC908GP32. The project has about 12K of machine code in the 32K flash of the microcontroller. This code has state machines for all or these functions:

1) Battery Level Monitoring as a low battery condition flashed an LED and ramped the outputs of the device down to a lower energy level to permit battery life extension.

2) Two separate state machines, one for each output channel of the device that managed a sensor that detected of the load for the channel was open or not and if so it slowly ramped the output for an open loaded channel to the off state, These state machines had timers that applied a low level output to the drive for a channel that was "open" every couple of seconds to try to determine of the load had been restored and if so the output was ramped back to the normal operating level.

3) There was a state machine that managed a software controlled charge pump to raise the battery voltage up to a high voltage around 120 V. The state machine managed a simple tracking voltage demand via an A/D converter.

4) There was a state machine involved with reading the settings of 8 pots from the user control panel and converting the values to internal variable settings at the correct times.

5) There was a state machine that managed the timing of the flashes on three LEDs. This was complicated becase the LEDs had to follow the operational cycles of the device in an On/Off manner but whiles they were ON still had to be able to flash of there was a warning state such as one of the loads being open as mentioned before.

6) There's more. Another state machine was used to manage the treatment cycle timing of the device that was set by the various POTs mentioned before. The pots set parameters such as output pulse rate, pulse width, Treatment ramp up time, treatment on time, treatment ramp down time, treatment cycle off time and the set amplitude for the two output channels.

7) There was a state machine that managed the interrupt driven keyboard scanner for a 7 switch input matrix.

8) Finally the main executive for the device was coded as a state machine. This managed such things as keypresses, mode chanages, remote test port access, external trigger input, and so forth.

What is that....9 state machines. Every project I do has them!!

Michael Karas