Method of upgrading a program, used in a data processing device having a permanent memory, from a version n to a version n+1 wherein, at any time, both recent version and previous version of the program are stored in a first (10) and a second (14) locations of said memory. Each one of version n and version n+1 of the program is using respectively configuration data of format n and format n+1 when it is used as current version. The configuration data of format n are automatically stored into said memory when version n+1 of said program is stored into said second location of memory.