it depends what you mean with "demo".
What should it demonstrate?
* simply existance and the name
* or do you think about an Intel Hex format (without meaningful contents)
* or should it contain a valid software that can be uploaded to a microcontroller
Hi all thanks for reply. Now I clearing what I want....
Suppose, I wrote code in microc avr for atmega8a and compiled. After compiled I got a hex. This hex i will give my client and I want after 6 month this hex will not work in atmega8a.
In a simple system it would be necessary to implement a local RTC, with battery removal check - once this would reverse the date. On a more robust system, you would need to have access to the world time server. By the way, I've done in the past a system that took advantage of the GPS to obtain the calibration of the system local date/time. This way it is possible to implement an expiration date for the program.
You could consider to sell chip already programmed with 'lock bits' set to disable Further programming of the Flash and EEPROM.
Then client couldn't workaround your timeout feature.
You could consider to sell chip already programmed with 'lock bits' set to disable Further programming of the Flash and EEPROM. Then client couldn't workaround your timeout feature.
In this case it would work fine for accounting the time in which the system were working, that is, the internal EEPROM could store the last updated count of the local RTC just updated, but if it is desired to determine a deadline for expiration of the trial, it would not be possible to ensure if the system was shutted down during evaluation period, therefore freezing time counting.
That's right, then the trial time would be described as time when the system is powered on and is working. The time when the system is shut down wouldn't be counted in this case.