I would follow behind Andy and suggest that the 'C420 part is way way more complex than many of the older Atmel parts. It is almost for sure that there is some combination of SFRs, programming fuse options, or memory layout configuration that needs to be taken care of to get the part to work in a way suitable to any particular application. And I can say that with confidence without even opening the 'C420 data sheet!! Rodrigo: Did you open the 'C420 data sheet? If not you are now facing the need to become very intimate with the part you have chosen to use.

Michael Karas