Electrical computers and digital processing systems: support – Clock – pulse – or timing signal generation or analysis – Multiple or variable intervals or frequencies
Reexamination Certificate
1998-12-10
2001-04-24
Heckler, Thomas M. (Department: 2182)
Electrical computers and digital processing systems: support
Clock, pulse, or timing signal generation or analysis
Multiple or variable intervals or frequencies
C710S071000, C713S502000
Reexamination Certificate
active
06223298
ABSTRACT:
The invention relates to interchanging data with an IC card.It relates more particularly to an improved communications interface between a processor unit, of the microprocessor type, and an IC card. The communications interface of the invention is designed for implementation in any apparatus having the function of interchanging data in transmission and/or in reception with an IC card, and in particular for implementation in a reader, a programmer, or a tester of IC cards.
BACKGROUND OF THE INVENTION
At present there are two types of IC cards: IC cards which essentially comprise a memory and are not fitted with a microprocessor or the like; IC cards which are fitted with a microprocessor, memory and inputs/outputs. The term “IC card” will refer hereafter to IC cards fitted with a microprocessor or the like.
The inputs/outputs of an IC card essentially comprise a both-way serial communications line for interchanging data with an external device, and a clock line (CK) enabling an external clock signal to be applied for the purpose of clocking the microprocessor of the IC card.
At present, IC cards are required to comply with international standard ISO 7816-3, which defines electrical characteristics. In compliance with that standard, each byte is transmitted over the serial communications line, and is put into the following serial format: a start bit (always 0), eight data bits D
0
to D
7
or D
7
to D
0
(in positive or negative logic), a parity bit (odd or even), and a stop bit. Each IC card is also characterized by an elementary time unit corresponding to the time required to transmit one bit on the serial communications line. This elementary time unit is abbreviated ETU in the above-mentioned standard, and for a given IC card it depends on a factor F/D and on the frequency Fs of the clock signal applied to the IC card. More precisely, the elementary time unit ETU in seconds for an IC card is given by the formula: ETU=(F/D)/Fs. Each IC card is given predetermined values for the parameters F and D. In particular, the above-mentioned standard specifies that the parameter F can take the following values: 372, 558, 744, 1116, 1488, 1860, 512, 768, 1024, 1536, and 2048, and that the parameter D can take the following values: 1, 2, 4, 8, 16, 32, 20, ½, ¼, ⅛, {fraction (1/16)}, {fraction (1/32)}, and {fraction (1/64)}. With certain types of IC card, the values for the parameters F and D can also be modified, thereby making it possible advantageously to modify the speed of dialog with the IC card.
There are two different ways in which data can be interchanged, in reception and/or transmission, between an IC card and an external device implementing a microprocessor, such as an IC card reader, a programmer, or a tester: purely software processor means implemented by the microprocessor of the external device; or an electronic interface implemented between the microprocessor of the external device and the IC card for the purpose of controlling communication with the IC card over the serial communications line of the IC card.
With purely software processing, the microprocessor of the external device must know the elementary time unit ETU of the IC card. On reception, the software implemented by the microprocessor of the external device is designed, for example, to scan the serial communications line of the IC card in order to detect the first start bit sent by the IC card over the serial communications line, so that starting from detection of the start bit, it samples the state of the serial communications line at predetermined time intervals corresponding to the elementary time unit ETU of the IC card, and finally, on reception, it takes the bits it has received and serializes (reconstitutes) the byte as transmitted by the card (data bits D
0
to D
7
). Implementing software type processing requires software timing to be simulated that is calibrated as a function of the frequency of the clock signal applied to the IC card and as a function of the parameters F and D, i.e. as a function of the elementary time unit ETU for which the IC card is configured. In addition, with software processing, serialization of the bits, e.g. to reconstitute a received byte, can be performed using a long elementary time unit ETU, e.g. equal to 104 &mgr;s, which corresponds to the conventional transmission speed of 9600 bauds, but which gives rise to problems with shorter elementary time units, particularly units that are of the order of a few microseconds. It is necessary for the microprocessor to have processing power that is sufficient to enable the instructions of the software to be performed within the time made available by the speed of dialog with the IC card. That is why the software solution for controlling data interchange with an IC card is suitable solely for applications that implement IC card dialog speeds that are low.
To dialog with an IC card at higher speeds, i.e. in other words with an IC card configured to use a shorter elementary time unit, it is preferred to adopt the second solution, i.e. to implement an electronic interface between the IC card and the microprocessor of the external device, which interface is designed to control communication with the IC card via the serial communications line of the IC card.
At present, all electronic communications interfaces for IC cards use data serialization means that enable a byte to be reconstituted on reception, and that enable a byte to be decomposed on transmission. As a general rule, such serialization means are made using a standard component of the ACIA, EPCI, . . . , type, dedicated to mode serialization, and associated with a crystal or an oscillator for clocking its operation. At present, the means for serializing data on transmission or on reception are clocked by a first clock signal at a predetermined fixed frequency delivered by a crystal or an oscillator, and the microprocessor of the IC card is clocked from a second clock signal which is applied to the clock line (CK) of the IC card.
Standard components available on the market and dedicated to serialization generally include programmable clock dividers and are thus capable of taking a clock signal at a fixed frequency which is applied thereto for clocking purposes, and operating at various transmission speeds which correspond to the speeds commonly used between computers, i.e. in practice the following baud rates: 300, 600, 9600, 19200, 38400, and 115200. Programming the transmission speed of the component to one of the above-mentioned values is usually performed by initializing a parameter to a predetermined value in a register of the component. Thus, in the above-mentioned presently-known communications interfaces, in order to be able to dialog between the standard component dedicated to serialization and the IC card, it is necessary to program both the communications speed of the standard component and the elementary time unit ETU of the IC card to values that are compatible. The elementary time unit ETU of the IC card can be programmed either (first solution) by loading appropriate values for the parameters F and D into the IC card, or else (second solution) by appropriate adjusting the frequency of the clock signal applied to the card so that the elementary time unit ETU of the card is compatible with the transmission speed of the serialization means.
At present, whichever solution is used, the main drawback of presently-known communications interfaces is that they are capable of dialog with an IC card only at a determined transmission speed which is fixed by the serialization means of the interface and which can take only a very limited number of values. Furthermore, these transmission speed values are relatively small, and in particular they D
0
not make it possible to dialog with an IC card at the maximum transmission capacity of the microprocessor of the IC card. For example, for a clock applied to the IC card at a frequency of 3.57 MHz, and for parameters F and D respectively equal to 372 and 1, the elementary time unit of the IC card is 104
Deroo Daniel
Talaga Michel
Tellier Vincent
Heckler Thomas M.
Micropross
Wolf Greenfield & Sacks P.C.
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