Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
1998-08-14
2002-01-15
Maung, Zarni (Department: 2154)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C711S152000, C712S043000
Reexamination Certificate
active
06339815
ABSTRACT:
TECHNICAL FIELD
The present invention relates to microcontroller systems having flash memory in a program memory address space and, in particular, to a microcontroller system that selectively allocates portions of the program memory space to either internal or external memories, or a combination thereof, for reasons of security of the internal memory contents.
BACKGROUND
Microcontroller systems including memory are known in the art. With a conventional microcontroller system, blocks of the memory may be locked such that a locked block cannot be interrogated. This locking thus secures program code contained in the locked blocks from unauthorized access by firmware piraters and from accidental erasing and programming.
However, conventionally, neither can the locked blocks be conveniently reprogrammed or accessed by an authorized user. It is desirable for a microcontroller system to be configurable such that blocks of memory ca be locked from unauthorized interrogation or code corruption, but can also be reprogrammed and/or accessed under a predetermined secure environment.
SUMMARY
In accordance with the present invention, a microcontroller system includes program memory space allocation means. In a first mode of operation, a first block of program memory is hidden for code fetching such that a processor is prohibited from retrieving program instructions from the first block of program memory. In a second mode, however, the first block of program memory is accessible for code fetching. In a third mode of operation, the program memory space allocation means allocates the program memory space such that the processor may retrieve program instructions only from an external memory, that is not unitarily formed in the integrated circuit. In some embodiments, the mode of operation of the program memory space allocation is controlled in response to the contents of a configuration register.
By having means to so allocate the program memory, the security of the program memory is enhanced.
REFERENCES:
patent: 5014191 (1991-05-01), Padgaonkar et al.
patent: 5067077 (1991-11-01), Wakimoto et al.
patent: 5251304 (1993-10-01), Sibigtroth et al.
patent: 5432950 (1995-07-01), Sibigtroth
patent: 5452431 (1995-09-01), Bournas
patent: 5465341 (1995-11-01), Doi et al.
patent: 5515540 (1996-05-01), Grider et al.
patent: 5557743 (1996-09-01), Pombo et al.
patent: 5737760 (1998-04-01), Grimmer, Jr. et al.
patent: 5809544 (1998-09-01), Dorsey et al.
patent: 5903912 (1999-05-01), Hansen
patent: 5911778 (1999-06-01), Garnett
patent: 5930826 (1999-07-01), Lee et al.
patent: 5954818 (1999-09-01), Dalvi et al.
patent: 6076149 (2000-06-01), Usami et al.
“P83CE558/P80CE558/P89CE558 Single-chip 8-bit microcontroller”, Preliminary Specification IC20 Data Handbook, Phillips Semiconductors, Aug. 6, 1996.
Feng Eugene
Phillips Gary
Chang Jung-won
Maung Zarni
Silicon Storage Technology, Inc.
LandOfFree
Microcontroller system having allocation circuitry to... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microcontroller system having allocation circuitry to..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microcontroller system having allocation circuitry to... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2826582