Process for loading a secure memory image for a microcontroller and assembly including a microcontroller

A process for loading a secure memory image for a startup procedure of a microcontroller from an external non-volatile memory, comprising the steps of

• (a) starting the microcontroller and reading by the microcontroller at least header information of a secure memory image;
• (b) analyzing the header information to determine whether it is faulty;
• (c) if the header information is error-free, reading by the microcontroller a data section of the memory image and analyzing the data section to determine whether it is faulty;
• (d) if the data section is error-free, executing the memory image by the microcontroller;
• (e) if the data section is faulty, placing the microcontroller in a locked state in which execution of any program is prevented pending a restart of the microcontroller;
• (f) detecting the locked state of the microcontroller by a controller located outside of the microcontroller;
• (g) instituting precautionary measures that lead to modified read-in data values of the memory image in a subsequent attempt by the microcontroller to read the memory image, said precautionary measures including modifying the read-in data values of the header information of a faulty memory image in the external non-volatile memory in such a way that the read-in header information appears to be faulty;
• and
• (h) initiating a restart of the microcontroller to cancel the locked state and to repeat at least steps (a) through (e).