Input- and Output-Level Specifications of 1.8V Core of SAM3X8E Microcontroller

There's also no reason for the internal circuitry to maintain the same sort of voltage thresholds (or hysteresis) that is expected from external pins.

Very interesting and inspiring information.

Traditionally, we (the maintenance/training engineers, amateur designers, and later teachers) have been bearing the mind-set of seeing the electronics logic gates from 5-V TTL/CMOS perspective. This is the first time we (myself and my pupils) are playing with 1.8V Core and 3.3V IO. Because the Arduino DUE is readily available and comparatively not so expensive, we find here a lot of opportunities to design/interfacing hand-made logic sifters rather than using factory-made dedicated logic sifters.

The data sheet of SAM3X8E is not organized and informative as the ATmega328P is. As we are proceeding with the studies and experiments of Arduino DUE, we are faced with many many conceptual questions. It is a matter of happiness that the DUE Members try their best to present rational opinions along with additional reading materials.

@wstfw

Your question of Post#1, from my view point, deserves much better answer and explanation/discussion than what I have presented in Post#2. I hope that other members including you may present some discussion on this issue.

BTW: Increasing speed: Does it refer to the lower time in the transition of H-to-L/L-to-H or Clock Period or both?