FR2791206A1 - METHOD FOR COMMUNICATING THE PARAMETERS OF A DIGITAL TRANSMISSION PROTOCOL - Google Patents

Abstract

The invention concerns a method for communicating parameters of a digital data transmission protocol between an equipment said to be a reference equipment and an equipment said to be a follower equipment so as to enable the follower equipment to be adapted to the transmission characteristics of the reference equipment In a first step, the reference equipment communicates with the follower equipment in standard mode to signal thereto that it can communicate according to another communication mode. At the request of the follower equipment, the characteristics of this new mode are transmitted by the reference equipment. Said characteristics are, for instance, the clock cycles (H28, H34, to H70, H94, H97) indicating the moments for sampling the bits b0, b1, to b7 of an octet. The invention is applicable to microcircuit card systems and to the corresponding terminals.

Description

-1

  PROCESS FOR COMMUNICATING THE PARAMETERS OF A PROTOCOL

DIGITAL TRANSMISSION

  The invention relates to a method for communicating the parameters of a digital transmission protocol between so-called "reference" digital transmission equipment such as an electronic chip card and so-called "follower" digital transmission equipment, for example a terminal. reading, to let him know the characteristic parameters of the desired transmission, it must be effected by taking as reference the performance of the reference equipment, that is to say the most modest. The process applies more particularly to the digital transmission process described in the French patent application filed on November 18, 1998 under the

number 98 14492.

  This process is characterized by a series of frames, each frame having, for example, the composition or the

format shown in Figure 1.

  Thus, each frame successively comprises, from start to finish, frame synchronization signals 10, data signals 12, control code signals

  data 14 and an end of frame signal 16.

  The synchronization signal is, for example, defined by the series of rectangular signals 20, 22, 24 and 26 (FIG. 2) the durations of which are respectively one clock cycle, two clock cycles, three cycles of clock and a constant number from one to many

tens of clock cycles.

  The data signals are, for example, in the form of bytes consisting of binary signals or bits b0, b1, b2, b3, b4, b5, b6 and b7 (Figure 3) whose binary values "1" or "0" are stable at characteristic instants IbO, Ibl, Ib2, Ib3, Ib4, Ib5, Ib6 and

Ib7, respectively (Figure 4).

  In the time intervals ITO to IT7, the signal of the value "1" or "0" of the bit is only present for a determined time and at a determined position in

this interval.

  The data control code signals 14 are similar to the data signals in their

presentation.

  Two consecutive elementary data or bytes are separated by a time interval or window 30 of fixed and constant duration which is used to transmit signaling signals such as an end of byte and / or end of frame signal 32 or a reception suspension signal 34, known as a data flow control known as "Xoff". These signals 32 and 34 have precise positions in this time interval 30 so as not to

to be confused with each other.

  So that such a sequence of signals forming a frame can be detected and understood by the tracking equipment, it is necessary that the latter know, on the one hand, the composition of the frame and, on the other hand, in this frame the moments he owes

  take into account the value of the binary signals.

  In current chip / terminal card systems, this information concerning the composition of the frame and the instants of value or sampling of the binary signals are known to the terminal (tracking equipment) by "construction". Therefore, it is difficult to change them in order to adapt them to the evolution of the technical characteristics of

reference equipment.

  Thus, if the technologies implemented in smart cards make it possible to increase the processing speed, this increase in speed cannot make it possible to increase the communication speed because the latter is "frozen" by the tracking equipment . In addition, in the current state of the systems used, it is difficult to make equipment with different communication speeds coexist since it is necessary for the tracking equipment to know the characteristics of each reference equipment.

  to which it is likely to be connected.

  The invention therefore relates to a method for communicating the parameters of a digital data transmission protocol between so-called "reference" equipment and so-called "follower" equipment so as to allow the follower equipment to adapt to the characteristics. for transmitting the reference equipment which comprises the following steps consisting in: (a) putting the reference equipment into transmission relation with the tracking equipment according to a communication protocol known to the two equipments, and (b) transmitting, from the reference equipment to the tracking equipment, information defining the characteristics of a particular digital transmission method which will be implemented by the reference equipment to transmit and to receive the data which

  will be exchanged between the two devices.

  Other features and advantages of this

  invention will appear on reading the description

  following of a particular example of realization of

  the invention, said description being made in relation

  with the accompanying drawings in which: - Figure 1 is a diagram showing the composition or format of a digital transmission frame to which the invention applies, - Figure 2 is a diagram showing, for the frame of Figure 1, a particular form of the frame synchronization signals, FIG. 3 is a diagram showing, for the frame of FIG. 1, a composition of the data signals and of the data control codes as well as the end signaling signal of frame when it exists, - Figure 4 is a diagram showing, for the frame of Figure 1, the synchronization signals, the data signals and the signaling signals of a frame in relation to the sampling instants of these signals, - Figure 5 is a table showing the information which is transmitted by the reference equipment to indicate to the tracking equipment the cycles of a clock signal defining the sampling instants in the equi pement follower of the signals received from the reference equipment, - Figure 6 is a table showing the information which is transmitted by the reference equipment to indicate to the tracking equipment the cycles of a clock signal defining the instants to which the tracking equipment must transmit the signals to the reference equipment, - Figure 7 is a table showing the information which is transmitted by the reference equipment to indicate to the tracking equipment another form of synchronization signal of frame different from that of FIG. 5, - FIG. 8 is a diagram showing an example of composition of a byte in a digital transmission protocol of the asynchronous type, and - FIG. 9 is a table showing the information which is transmitted by the reference equipment to the follower equipment to indicate the characteristics of its asynchronous transmission protocol. The method for communicating the parameters of a digital transmission protocol from a reference equipment to a tracking equipment will be described in particular in its application to a digital transmission frame which has been presented in the preamble in relation to FIGS. 1 to 4 , these Figures 1 to 4 forming an integral part of the

description of the invention.

  The invention will be described in its application to a microcircuit card, also called an electronic chip card, which is capable of communicating with a terminal, such as a cash dispenser, by means of digital signals transmitted by galvanic, radioelectric, inductive or optical connections. However, it applies to any communication or transmission of digital signals between two pieces of equipment, of the type

synchronous or asynchronous.

  In the following description, the card to

  microcircuit will be called "reference equipment" while the terminal will be called "tracking equipment" to indicate that the terminal communicates with the microcircuit card according to a mode or process imposed by

  the latter which constitutes the "reference".

  It should be noted that the terminal and the microcircuit card are in turn transmitter equipment and receiver equipment and share the same clock signal supplied by the terminal, which allows synchronism. The invention applies in particular to the digital transmission method described succinctly in the

  preamble and which corresponds to the detailed description

  which was made of it in the aforementioned patent application.

  FIG. 4 shows, in addition to the synchronization, data and signaling signals, the instants at which these signals must be sampled in order to know their value. These times are listed: - Isl, Is2 and Is3 for the synchronization signals, - IbO, Ibl, Ib2, Ib3, Ib4, Ib5, Ib6 and Ib7 for the signals of a byte of a frame, -IsigO and Isigl for , respectively, the end of frame or byte signal and for the signal of suspension of reception, called flow control

  known as "Xoff".

  These instants are defined by the rank of the cycles of a clock signal from an initial instant (start of frame), clock signal which is common to the microcircuit card and to the terminal to which it is connected.

and which is provided by the terminal.

  The table in Figure 5 corresponds, for example, to

  times of issue of the microcircuit card, that is

  ie the instants at which the terminal must sample the signals received from the microcircuit card. It indicates in the first column the list of sampling instants and in the second column the ranks of the clock cycles to which they must appear. In the second column, the rank is indicated by a number, the capital letter H and L indicating the part of the clock cycle ("High" H or "Low" L) in which the sampling must be carried out. The table in FIG. 6 then corresponds to the instants of reception of the microcircuit card, that is to say the instants at which the terminal must transmit in order to be understood, on reception, by the microcircuit card. Each table also includes an additional line called "Ibyte" to indicate the duration separating the beginnings of two consecutive bytes, this duration encompassing the duration of one byte and that reserved for signaling signals. The values shown in the tables of Figures 5 and 6 are very similar in that the synchronization and signaling signals are identical while the data and byte duration (Ibyte) signals are slightly different. However, the invention can be implemented with very different synchronization and signaling values on transmission (FIG. 5) and on reception (FIG. 6) but also with very inter-byte data and duration values.

different.

  Thus, the table in FIG. 7 corresponds to that in FIG. 5 but with a very different synchronization signal in the sense that no rank of clock is indicated for the times Isl, Is2 and Is3, which is materialized with the value "0". Such a synchronization signal means that the terminal must only take account of the falling edge of the signal emitted by the microcircuit card, this edge indicating the start of

counting clock signals.

  In order for the "follower" equipment to be able to apply the conventions listed in the tables of FIGS. 5 and 6, the invention provides that the microcircuit card transmits them to the terminal at the

request of the latter.

  When a terminal receives the information contained in these tables of FIGS. 5 and 6, it records it so as to use it for any future communication with this microcircuit card or any other card of the same family, upon receipt and

on the show.

  More specifically, during the first communication between a new microcircuit card having a new transmission mode according to the invention and a terminal, the new card informs the terminal in the transmission mode T = O, for example, that 'she can communicate in another way. When the terminal recognizes that this is another mode which it does not know, it sends an instruction to read the tables in FIGS. 5 and 6 from the card, save them in its memory and use them to initialize a transmission

  following the new mode with this card.

  Since the information in the tables in FIGS. 5 and 6 is saved in the terminal, the transfer of these tables is no longer necessary when the terminal recognizes that it is a card

  operating in this new mode.

  The invention has been described in relation to a microcircuit card able to communicate with a terminal according to a synchronous mode and a transmission method.

  digital described in the aforementioned patent application.

  However, the invention is applicable to an asynchronous mode, in which case the information to be transmitted from the reference equipment to the tracking equipment concerns the structure of the frame and not the

sampling moments.

  Figure 8 is an example of a byte structure in an asynchronous protocol. It includes byte start bits "DB", data bits B0 to B7 in a certain order, starting for example with the most significant bit, ie B7, "PA" bits for checking the integrity of the data conveyed, for example the

  parity, and stop bits "STOP".

  It should be noted that a frame in asynchronous protocol

can consist of several bytes.

  The table in FIG. 9 indicates the information that the reference equipment must supply to the tracking equipment so that the latter can correctly analyze the frames it receives from the reference equipment or send frames which are correctly analyzed by

reference equipment.

  The information to be transmitted is, for example: (a) -the rank of the first bit of data transmitted, for example the seventh, that is to say B7, (b) -the voltage level "HIGH" or "LOW "which corresponds to the binary digit" 0 ", (c) - the parity for the message integrity check, either" PAIR "," ODD "or" NONE ", (d) - the number of bits of a data , for example eight, (e) -the number of stop bits "STOP", for example two, (f) -the possibility of repeating the byte in the event of parity error, "YES" or "NO" , (g) -the number of cycles of the clock signal per elementary time unit "ETU" corresponding to one bit, for example thirty-two, (h) -the minimum number of cycles of the clock signal between two bytes consecutive, for example four, (i) -an information indicating the maximum waiting time better known by the English expression "TIME OUT", this time being expressed in clock cycles, for example eighty, 0 ) -the maximum size of data blocks, for example, so sixty-four, o (k) -baud rate expressed in baud, by

example 9,600.

  In the table in FIG. 9, the "Reception" column indicates the reception characteristics of the reference equipment, these characteristics having to be implemented on transmission by the equipment.

  follower to be understood from the reference equipment.

  Similarly, the "Transmission" column indicates the transmission characteristics of the reference equipment, these characteristics to be implemented on reception by the follower equipment to receive messages from the reference equipment. Note that some of the characteristics of the table in Figure 9 are not necessary, for example those of rows (b), (f), (h), (i), (j) or (k). It follows that the minimum number of characteristics to be transmitted are (a), (c), (d), (e), to which it

add (g) or (k).

  It should be noted that the tables in FIGS. 5, 6, 7 and 9 are, for example, in the form of computer files which are transmitted to the tracking equipment at the latter's request, for example via a reading instruction in

  source of tracking equipment.

Claims (17)

R E V E N D I C A T I ON S   1. Method for communicating the parameters of a digital data transmission protocol between so-called "reference" equipment and so-called "follower" equipment so as to allow the follower equipment to adapt to the transmission characteristics of the 'reference equipment which comprises the following steps consisting in: (a) putting the reference equipment into transmission relation with the following equipment according to a communication protocol known to both equipment, and (b) transmitting, equipment of reference to the tracking equipment, information defining the characteristics of a particular digital transmission method which will be implemented by the reference equipment to transmit and to receive the data which   will be exchanged between the two devices.   2. Method according to claim 1, characterized in that during step (a), the reference equipment indicates to the tracking equipment that it can communicate according to said particular digital transmission method. 3. Method according to claim 2, characterized in that during step (b), the tracking equipment is transmitted by the reference equipment the characteristics of said transmission method   particular digital if he doesn't know it.   4. Method according to claim 2, characterized in that during step (b), the tracking equipment implements said particular digital transmission method if it knows of a previous transmission relationship with a reference equipment having   the same particular digital transmission process.   5. Method according to any one of the claims   above 1 to 4, characterized in that the characteristics of the particular digital transmission method are recorded in the reference equipment and are accessible for reading by tracking equipment.   6. Method according to any one of the claims   previous 1 to 5, characterized in that the characteristics of the particular digital transmission method are different depending on the direction of the   digital data transmission.   7. Method according to any one of the claims   above 1 to 6, in its application to a particular digital transmission method of the synchronous type, characterized in that the transmission characteristics are defined by the ranks (Hl, H3, L6, H28, H34, etc.) of the cycles of the signal d clock to which the values of the synchronization, data, control and signaling signals of a frame are transmitted and by the number of cycles of the clock signal defining the reserved duration (Ibyte) to each byte in a frame.   8. Method according to any one of claims 1   to 6 in its application to a particular digital transmission method of the asynchronous type, characterized in that the transmission characteristics are defined at least by the composition of the frame of bytes of each of the bytes of the frame as well as by   the bit rate of each byte.   9. Method according to claim 8, characterized in that the transmission characteristics are defined by at least: - the rank of the first bit of data which will be transmitted, - the data control code, - the number of bits of each data , - the number of stop bits, - the number of cycles of the clock signal per unit of elementary time.   10. Method according to claim 8, characterized in that in the transmission characteristics the number of cycles of the clock signal per elementary time unit is replaced by a transmission speed. 11. Method according to claim 9 or 10, characterized in that the transmission characteristics further comprise a minimum number of inter-byte cycles.   12. Method according to one of claims 9 to 11,   characterized in that the transmission characteristics also include a level value (Up / Down) corresponding to the binary value! 0 ".   13. Method according to one of claims 9 to 12,   characterized in that the transmission characteristics further include a maximum waiting time.   14. Method according to one of claims 9 to 13,   characterized in that the transmission characteristics further include a new test of Byte transmission.   15. Method according to one of claims 9 to 14,   characterized in that the transmission characteristics further include a maximum size data blocks.   16. Electronic chip card characterized in that it implements the method according to any one of   previous claims 1 to 15.   17. Reading terminal for an electronic chip card characterized in that it implements the method according to   any one of the preceding claims 1 to 15.