The fact, that "transient voltage spec is not listed in the i.MX6D/Q spec" means that any voltages outside of
specified range are disabled, assuming that only ramp from 0.0 V during power up is allowed.
Moreover, please pay attention on the following footnote in i.MX6 Datasheet regarding IO pins:
"Overshoot and undershoot conditions (transitions above OVDD and below GND) on switching pads must be held below 0.6 V, and the duration of the overshoot/undershoot must not exceed 10% of the system clock cycle. Overshoot/ undershoot must be controlled through printed circuit board layout, transmission line impedance matching, signal line termination, or other methods. Non-compliance to this specification may affect device reliability or cause permanent damage to the device.
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