I am sure that some derivatives have parasitic diodes on the inputs (it seems that any chip, uC or not has a bunch of them) but relying on parasitic diodes for protection is dangerous since no manufacturer would test for such.

However, the 74HC/T family has defined protection diodes (20mA) as seen in

http://www.philipslogic.com/support/t...hcspec.pdf

and it may be more economical/compact to use a 74HCT chip than diodes to protect inputs


Erik