80C52 with Secret ROM
Matra MHS offers 80C52 with the encrypted secret ROM
option to secure the ROM code contained in the 80C52
The clear reading of the program contained in the ROM
is made impossible due to an encryption through several
random keys implemented during the manufacturing
The keys used to do such encryption are selected
randomwise and are definitely different from one
microcontroller to another.
This encryption is activated during the following phases :
– Everytime a byte is addressed during a verify of the
ROM content, a byte of the encryption array is
– MOVC instructions executed from external program
memory are disabled when fetching code bytes from
– EA is sampled and latched on reset, thus all state
modification are disabled.
For further information please refer to the application
note (ANM053) available upon request.
80C52 with Secret TAG
Matra MHS offers special 64-bit identifier called
“SECRET TAG” on the microcontroller chip.
The Secret Tag option is available on both ROMless and
The Secret Tag feature allows serialization of each
microcontroller for identification of a specific
equipment. A unique number per device is implemented
in the chip during manufacturing process. The serial
number is a 64-bit binary value which is contained and
addressable in the Special Function Registers (SFR) area.
This Secret Tag option can be read-out by a software
routine and thus enables the user to do an individual
identity check per device. This routine is implemented
inside the microcontroller ROM memory in case of
masked version which can be kept secret (and then the
value of the Secret Tag also) by using a ROM Encryption.
For further information, please refer to the application
note (ANM031) available upon request.
Rev. E (31/08/95)