1.3. Auto Start Using MAX II Devices
The detailed description of the implementation is based on the MAX II devices. This application can also be implemented in MAX V and MAX 10 devices.
You can implement this design example with an EPM240 or any other device, supporting external RC circuitry, a power supply that is capable of shut down, and two capacitors on the GPIO pins to act as ‘memory’ devices that save previous states. Implementation involves using the design example source code and allocating the appropriate signals and control lines to the GPIO lines of the MAX II device, along with its support circuitry. The MDN-B2 demo board has a built-in support circuitry.
To demonstrate the control of the power cycle, two capacitors (C9 and C10 on the MDN-B2 demo board) and four LEDs (D2, D3, D5, and D6) are used. This design reads the values from the capacitors as soon as the MAX II is powered on.
|Capacitor C9||Capacitor C10||LED|
For each set of values, the corresponding LED glows. The MAX II then increments the count and writes back this value to the capacitors. The write cycle continues for some time to ensure sufficient charging of the capacitors. The power down and its complement signals are made high and low, respectively, resulting in complete power down.
Upon subsequent power on after a period of time determined by the external RC, the MAX II repeats the cycle of reading, LED display, and updating the capacitor states before powering down again. Observing the LED counting up demonstrates the Auto Start feature of this design.
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