How to read suffix of part nr for example 68HC711K4CFN4 replaceable by CFN3?

Discussion created by COR WATER on Apr 19, 2007
Latest reply on Apr 20, 2007 by COR WATER
Sorry if this is documented here already, I tried several searches and could not find any
difference in specs between a processor part nr
68HC711K4CFN3 and the (original) CFN4 that is in the controller.
This is for an Electric Vehicle (US Electricar) which has a 50 kW 3-phase AC drivetrain made by Hughes,
unfortunately information is scarce and the CFN4 parts are hard to find,
but CFN3 are plentiful.
Anybody able to enlighten me?