the AD719x (and other) data sheets specify digital input voltages 0,3V beyond rails and digital input current of 10mA. I assume, this is an "OR" specification, since 10mA will only flow if the voltage exceeds 0,3V beyond rails.
But this is only an absolute maximum, there is no statement whether the operation is influenced by injected currents.
Is there a specification about influence of injected currents on measurement results?
Especially when driven from long lines (ADC on remote board), it's not easy to completely avoid overshoot / undershoot on digital lines,even with termination.
Competitor's data sheets explicitly warn that over-/undershoot "can severely disturb the analog to digital conversion process".