Signature Bytes
All Atmel microcontrollers have a three-byte signature code which identifies the device. This code can be read in both serial and parallel mode, also when the device is locked. The three bytes reside in a separate address space.
Wenn du also 0xff liest, dann funzt entweder dein HV-Progger net, oder du hast die signature bytes tatsächlich überschrieben, d.h. das Teil frittiert...