Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Patent
1996-07-29
1999-10-05
Chan, Eddie P.
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
235380, 235382, 902 26, 713200, G06F 1214, G06K 19073
Patent
active
059639806
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to portable integrated circuit cards, also known as chip cards. More particularly, it pertains to cards that have both a memory and a microprocessor to perform application programs contained in the memory. For example, an application program may be a monetary transaction program for a card designed for a banking application.
2. Description of the Prior Art
The general architecture of an integrated circuit chip contained in the card is most usually of the type shown in FIG. 1. The microprocessor is designated by the reference CPU and it is connected to a linking bus, which is furthermore connected to the memories of the card. These memories may be of different types and, most usually, memories of different types are present simultaneously in the integrated circuit. In particular, there may be a read-only memory (ROM) referenced MSYS to contain in particular the fixed programs constituting the general operating systems of the card, a non-volatile memory MU, an electrically programmable memory (EPROM) and possibly an electrically erasable programmable memory (EEPROM) to contain for example application programs and data elements to be kept from one session of use to another, and finally a volatile working memory (RAM) referenced MT containing data elements and portions of programs that are useful during the performance (i.e., execution) of the application programs but are not kept when the card is not used. (Herein, the terms "perform" and "execute" are used interchangeably.)
The integrated circuit also has a communications circuit COM for communications (generally serial communications) between the microprocessor and an input/output terminal I/O of the integrated circuit with a view to exchanges with the exterior of the chip card. The other terminals of the integrated circuit may, in a standard way, be supply terminals (VCC, GND), a clock terminal (CLK), a reset terminal (RST), etc. The functions of the terminals present depend on the communications protocols used.
The general architecture of the integrated circuit may also comprise safety devices DS.
The different memories may, under certain conditions indicated here below, be accessible through the microprocessor CPU to perform the following operations: contained at a determined address.
The read-only memory MSYS may be called a system memory in view of the basic operation programs that it contains. These are programs that all the application programs must make use of so that the card may function. This is the central software core of the card. It is fixed and this is why it is made by means of a non-modifiable read-only memory technology. The information elements and programs that it contains are of a confidential type (usually, the manufacturer of the chip does not wish the programs of the card operating system to be known). This memory therefore is not at all accessible in write mode and it is desirable that it should not be accessible in read mode either. It is of course accessible for the performance of instructions.
The non-volatile memory MU contains data elements and programs that are modifiable. It may be called a "user memory" because it contains specific data and specific programs of an application that concerns the user. However the data elements that it contains are confidential in varying degrees and this is why it is most usually sought to divide this memory into zones with varying degrees of reserved access: these may be zones that are accessible in write mode but not in read mode or accessible in read mode but not in write mode or again zones that are completely accessible or completely inaccessible. Furthermore, certain zones have to be capable of containing program instructions that can be performed by the microprocessor of the card while other zones should not be capable of containing such instructions.
The working memory MT contains temporary data elements which may result from the performance of the programs of the operating system or of the application progr
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Coulier Charles
Gordons Edouard
Grimonprez Georges
Chan Eddie P.
Encarnacion Yamir
Gemplus Card International
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