Microprocessor-based memory card that limits memory accesses by application programs and method of operation
US5963980A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 29, 1996 |
| Grant date | Oct 5, 1999 |
| Priority date | — |
| Expiry date | Jul 29, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06Q20/3576
- WIPO fieldIT methods for management
- WIPO sectorElectrical engineering
Abstract
Microprocessor-based cards use application programs contained in a non-volatile user memory (MU), under the control of an operating system in a read-only memory (MSYS). To provide flexibility and security of access to the various memory zones without using a specific rigidly fixed circuitry, it is proposed that the memory access instructions of the application programs (PG1, PG2, PG3) should be interpreted and not performed directly. The interpreter is in the read-only memory (MSYS) or in the user memory and it carries out an access instruction as follows: it explores a reserved zone (ZR) of the user memory to find out if the requested access (access for reading, writing or performance) is cleared for the requested address. It performs the instruction only if the clearance is present. The reserved zone (ZR) which contains these clearances is updated during the writing, in the user memory, of a new application program. The updating can be done only by the operating system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.