Contactless transponder and method

Abstract

According to one aspect, a contactless transponder comprises a memory, an antenna configured to receive signals, a contactless interface coupled to the antenna and configured to emit memory access requests according to the signals received, a wired interface configured to receive memory access requests, an arbitration module configured to authorize access to the memory either for access requests emitted by the contactless interface or for access requests received by the wired interface, and wherein the wired interface is also configured to receive shutdown controls and transmit these shutdown controls to the arbitration module, the arbitration module being configured to be able to shut down the contactless interface when it receives a shutdown control.

Claims

1. A contactless transponder comprising: a memory; an antenna configured to receive signals; a contactless interface coupled to the antenna and configured to emit first memory access requests according to the signals received; a wired interface configured to receive second memory access requests, receive shutdown controls, and transmit the shutdown controls to an arbitration module; and the arbitration module, configured to: authorize access to the memory either for the first memory access requests emitted by the contactless interface or for the second memory access requests received by the wired interface; shut down the contactless interface when receiving a shutdown control initiated by a master module and received via the wired interface, so as to authorize exclusive access to the memory for the second memory access requests received from the master module via the wired interface; and after shutting down the contactless interface and while the contactless interface is shut down, generate an interrupt signal indicating the contactless interface is shut down, and transmit the interrupt signal to an output of the contactless transponder.

2. The contactless transponder according to claim 1, wherein the wired interface is also configured to receive reactivation controls and transmit the reactivation controls to the arbitration module, the arbitration module being configured to reactivate the contactless interface when it receives a reactivation control.

3. The contactless transponder according to claim 2, wherein the wired interface is configured to receive controls including an address and useful data, the reactivation control being a control including only an address dedicated to the reactivation control and a read/write bit.

4. The contactless transponder according to claim 3, wherein the reactivation control is represented by a single byte.

5. The contactless transponder according to claim 1, wherein the arbitration module is configured to receive a piece of information on a state of a write access to the memory by the contactless interface, and, when the shutdown control is received while the write access to the memory by the contactless interface is in progress, to wait for the write access to be completed to shut down the contactless interface.

6. The contactless transponder according to claim 1, wherein the wired interface is configured to receive controls including an address and useful data, the shutdown control being a control including only an address dedicated to the shutdown control and a read/write bit.

7. The contactless transponder according to claim 6, wherein the shutdown control is represented by a single byte.

8. The contactless transponder according to claim 1, wherein the wired interface is adapted to be coupled to an I.sup.2C bus.

9. The contactless transponder according to claim 1, capable of exchanging information items via the antenna with an external contactless reader, according to a contactless communication protocol compatible with near filed communication or radio frequency identification technology.

10. A system comprising: a contactless transponder comprising: a memory; an antenna configured to receive signals; a contactless interface coupled to the antenna and configured to emit first memory access requests according to the signals received; a wired interface configured to receive second memory access requests, receive shutdown controls, and transmit the shutdown controls to an arbitration module; and the arbitration module, configured to: authorize access to the memory either for the first memory access requests emitted by the contactless interface or for the second memory access requests received by the wired interface; shut down the contactless interface when receiving a shutdown control from a master module via the wired interface, so as to authorize exclusive access to the memory for the second memory access requests received from the master module via the wired interface; after shutting down the contactless interface and while the contactless interface is shut down, generate an interrupt signal indicating the contactless interface is shut down, and transmit the interrupt signal to the master module; and the master module, coupled to the wired interface of the contactless transponder, the master module configured to: initiate a shutdown of the contactless interface by sending the shutdown control to the contactless transponder via the wired interface; and send the second memory access requests to the arbitration module via the wired interface, after receiving the interrupt signal from the arbitration module of the contactless transponder.

11. The system according to claim 10, wherein the master module is a microcontroller.

12. The system according to claim 10, wherein the wired interface is also configured to receive reactivation controls and transmit the reactivation controls to the arbitration module, the arbitration module being configured to reactivate the contactless interface when it receives a reactivation control.

13. The system according to claim 10, wherein the arbitration module is configured to receive a piece of information on a state of a write access to the memory by the contactless interface, and, when the shutdown control is received while the write access to the memory by the contactless interface is in progress, to wait for the write access to be completed to shut down the contactless interface.

14. The system according to claim 10, wherein the wired interface is configured to receive controls including an address and useful data, the shutdown control being a control including only an address dedicated to the shutdown control and a read/write bit.

15. The system according to claim 14, wherein the shutdown control is represented by a single byte.

16. A method for managing access to a memory of a transponder comprising an antenna configured to receive signals, a contactless interface coupled to the antenna and configured to emit first memory access requests according to the signals received, a wired interface configured to receive second memory access requests, and an arbitration module, configured to authorize access to the memory either for the first memory access requests emitted by the contactless interface or for the second memory access requests received by the wired interface, the method comprising: receiving, by the wired interface, a shutdown control initiated by a master module; transmitting the shutdown control to the arbitration module; shutting down the contactless interface by the arbitration module, so as to authorize exclusive access to the memory for the second memory access requests received from the master module via the wired interface; and after shutting down the contactless interface and while the contactless interface is shut down: generating, by the arbitration module, an interrupt signal indicating the contactless interface is shut down; and transmitting, by the arbitration module, the interrupt signal to an output of the transponder.

17. The method according to claim 16, wherein, when the shutdown control is received while a write access to the memory by the contactless interface is in progress, a shutdown of the contactless interface is carried out after the write access is completed.

18. The method according to claim 16, further comprising, after shutting down the contactless interface: receiving a reactivation control via the wired interface; transmitting the reactivation control to the arbitration module; and reactivating the contactless interface by the arbitration module.

19. The method according to claim 16, further comprising receiving, by the wired interface, controls including an address and useful data, the shutdown control being a control including only an address dedicated to the shutdown control and a read/write bit.

20. The method according to claim 19, wherein the shutdown control is represented by a single byte.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages and features of the invention will become apparent upon examining the detailed description of implementations and embodiments, which are in no way limiting, and the appended drawings wherein:

(2) FIG. 1 illustrates a system comprising a contactless transponder and a master module;

(3) FIG. 2 illustrates a memory access management method;

(4) FIGS. 3-7 illustrate timing diagrams for various memory access management examples; and

(5) FIG. 8 illustrates a connected object comprising the system of FIG. 1.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(6) FIG. 1 schematically illustrates a system SYS according to one embodiment. The system SYS is configured to communicate with a contactless reader LSC.

(7) The contactless reader LSC can for example be an external contactless communication apparatus, for example a multifunction mobile telephone, better known as “smartphone”.

(8) The contactless reader LSC comprises an antenna ANTL.

(9) The system SYS comprises a contactless transponder TRS and a master module MM.

(10) The master module MM is a processing unit, for example a microcontroller.

(11) The transponder TRS can be a tag or a card.

(12) The transponder TRS acts as a gateway between the master module MM and the contactless reader LSC.

(13) The transponder TRS comprises an antenna ANT configured to receive radio frequency signals RAD emitted by the contactless reader LSC.

(14) In particular, the transponder TRS is capable of exchanging information items via the antenna ANT with a contactless reader LSC, according to a contactless communication protocol, for example compatible with the NFC or RFID technology.

(15) NFC technology is an open technological platform standardized in the standard ISO/IEC 18092 and ISO/IEC 21481 and incorporates many already existing standards such as for example ISO 14443 or ISO 15693 used for communication protocols.

(16) When transmitting an information item between the reader LSC and the transponder TRS, the reader LSC generates a magnetic field through its antenna ANTL which is typically a 13.56 MHz sine carrier wave. The pieces of information are communicated by an amplitude modulation of the carrier.

(17) The transponder TRS comprises a contactless interface IR coupled to the antenna ANT.

(18) The contactless interface IR includes in particular a demodulator (not shown) adapted to demodulate the received radio frequency signals in order to obtain the data transmitted from the reader LSC.

(19) The transponder TRS further comprises a wired interface IF coupled to the master module MM via a bus BI. Preferably, the bus BI is an I.sup.2C bus. Alternatively, the bus BI can be of the SPI (Serial Peripheral Interface) type for example.

(20) In particular, the bus BI includes two bidirectional lines. A first SDA line is configured to transmit data. The second SCL line is a synchronization clock line.

(21) The contactless transponder TRS also comprises a memory MEM, in particular a non-volatile memory. The memory MEM can for example be an EEPROM memory.

(22) The contactless reader LSC is configured to emit requests for access of the transponder TRS to the memory MEM. These access requests are transmitted to the transponder TRS via radio frequency signals RAD which can be received by the antenna ANT of the transponder TRS.

(23) The contactless interface IR is configured to receive memory MEM access requests resulting from the radio frequency signals received by the antenna ANT and coming from the contactless reader LSC.

(24) The contactless interface can be in an activated or shut down state. The state of the contactless interface is memorized in a register.

(25) The master module MM is also configured to emit requests for access of the transponder LSC to the memory MEM and transmit them to the wired interface IF via the bus BI.

(26) The wired interface IF is therefore configured to receive requests for access to the memory MEM emitted by the master module MM.

(27) Nevertheless, the memory MEM cannot be accessed simultaneously by the access requests received by the wired interface IF and by the access requests received by the contactless interface IR.

(28) The transponder TRS then comprises an arbitration module MA allowing to manage access to the memory MEM.

(29) The arbitration module MA can be a logic circuit.

(30) The arbitration module MA is coupled to the wired interface IF, to the contactless interface IR, and to the memory MEM. The arbitration module MA can thus receive the access requests coming from the wired interface IF and from the contactless interface IR then transmit them to the memory MEM.

(31) Moreover, the master module MM is also configured to emit shutdown controls and transmit them to the wired interface IF through the bus BI.

(32) The wired interface IF is configured to receive shutdown controls and transmit them to the arbitration module MA.

(33) The arbitration module MA is configured to receive shutdown controls from the wired interface IF and to shut down the contactless interface IR after receiving such a shutdown control.

(34) Shutting down the contactless interface IR prevents the contactless reader LSC from accessing the memory MEM of the transponder TRS. Access requests emitted by the contactless reader LSC are then ignored.

(35) The master module then has exclusive access to the memory.

(36) In particular, the transponder TRS is configured to shut down the contactless interface IR as soon as the master module MM indicates that it wishes to access the memory MEM by transmitting the shutdown control to the wired interface IF of the transponder TRS. By shutting down the contactless interface IR, the latter can no longer access the memory MEM.

(37) In this way, the master module MM obtains exclusive access to the memory MEM.

(38) The contactless interface IR can therefore no longer block access of the master module MM to the memory MEM.

(39) Such a transponder TRS is therefore robust against attacks by repeated access requests from a contactless reader LSC.

(40) More particularly, the arbitration module MA is configured, when it receives a shutdown control while a write access by the contactless interface IR to the memory MEM is in progress, to wait for this write access to be completed to shut down the contactless interface IR.

(41) The arbitration module MA is therefore configured to prevent memory MEM corruption that may occur when the contactless interface IR is shut down before writing is complete.

(42) Preferably, the shutdown control is a control including only an address dedicated to this shutdown control and a read/write bit.

(43) The shutdown control then has a simple structure. This structure is adapted to be transmitted by an I.sup.2C type bus BI.

(44) Because a dedicated address is chosen for this shutdown control, the shutdown control is not seen as a memory access request by the transponder TRS. Thus, the shutdown control has no effect on the processing of memory access requests passing through the bus BI.

(45) Advantageously, the shutdown control is represented by a single byte, the address dedicated to the shutdown control being represented on 7 bits.

(46) The shutdown control is then quick to transmit.

(47) Moreover, the arbitration module MA is configured to generate an interrupt signal INT and to transmit this interrupt signal to an output O1 of the transponder TRS after shutting down the contactless interface IR after receiving a shutdown control.

(48) The output O1 is then configured to transmit the interrupt signal INT to an input I1 of the master module MM via a wired connection between the output O1 and the input I1.

(49) The interrupt signal INT allows informing the master module MM that the contactless interface IR is shut down. The interrupt signal INT therefore allows indicating to the master module MM that its requests for access to the memory MEM can be processed.

(50) The master module MM therefore does not have to regularly send requests for access to the memory MEM until a memory MEM access request is granted. The master module MM simply waits to receive the interrupt signal INT to know that it can emit requests for access to the memory MEM after emitting the shutdown control.

(51) Because the master module MM simply has to wait to receive the interrupt signal INT, the power consumption of the master module MM is reduced. Furthermore, time can be saved because the interrupt signal INT indicates the moment from which an access request can be emitted and granted.

(52) In addition, the traffic on the bus BI is reduced.

(53) Moreover, the master module MM is also configured to emit reactivation controls and transmit them to the wired interface IF through the bus BI.

(54) The arbitration module is configured to receive reactivation controls from the wired interface IF and to reactivate the contactless interface IR after receiving such a reactivation control.

(55) Reactivating the contactless interface IR allows the contactless reader LSC to re-access the memory MEM of the transponder TRS. Access requests from the contactless interface IR are therefore no longer ignored.

(56) Preferably, the reactivation control is a control including only an address dedicated to this reactivation control and a read/write bit.

(57) The reactivation control then has a simple structure. This structure is adapted to be transmitted by an I.sup.2C type bus BI.

(58) In particular, the address used for the reactivation control is different from that used for the shutdown control.

(59) Because a dedicated address is chosen for this reactivation control, the reactivation control is not seen as a memory access request by the transponder TRS. Thus, the reactivation control has no effect on the processing of memory access requests passing through the bus BI.

(60) Preferably, the reactivation control is represented by a single byte, the address dedicated to the reactivation control being represented on 7 bits.

(61) The reactivation control is then quick to transmit.

(62) Alternatively, or in combination, the arbitration module can be configured to be able to reactivate the contactless interface when the wired interface is deactivated (in particular when a wired power supply is cut).

(63) FIG. 2 illustrates a memory access management method that can be implemented by the transponder TRS described above.

(64) In step 20, the arbitration module MA receives a shutdown control received by the wired interface IF and coming from the master module MM.

(65) If the contactless interface IR is in the process of performing a write access to the memory MEM when the arbitration module MA receives the shutdown control, then the arbitration module MA waits in step 21 for this write access to be completed then shuts down the contactless interface IR in step 22.

(66) Otherwise, the arbitration module MA shuts down the contactless interface IR by going directly to step 22 upon receiving the shutdown control if the contactless interface IR is not in the process of performing a write access to the memory MEM.

(67) After shutting down the contactless interface IR in step 22, the arbitration module MA generates the interrupt signal INT in step 23 and transmits it to the wired interface IF. This interrupt signal is transmitted to the output O1 of the transponder TRS. This interrupt signal is then sent to the input I1 of the master module MM through the wired connection between the input I1 of the master module and the output O1 of the transponder TRS. The interrupt signal is used to indicate to the master module MM that it has exclusive access to the memory MEM.

(68) The contactless interface IR remains shut down in step 24 until the arbitration module MA receives a reactivation control received by the wired interface IF and coming from the master module MM.

(69) Once the reactivation control is received, the arbitration module reactivates the contactless interface in step 25.

(70) Alternatively, the arbitration module can reactivate the contactless interface when the wired interface is deactivated (in particular when a wired power supply is cut).

(71) FIGS. 3 to 7 illustrate examples of implementation of the memory access management method described above. In these figures, the signal 100 represents the radiofrequency controls received and emitted by the contactless interface IR, the signal 101 represents the shutdown controls received by the wired interface IF, the signal 102 represents a state of write access to the memory MEM by the contactless interface IR (the high state of the signal indicating that a write access is in progress and the low state indicating that no write access is in progress), the signal 103 represents the state of the contactless interface (the high state of the signal indicating that the contactless interface is activated and the low state indicating that the contactless interface is shut down), and the signal 104 represents the interrupt signal (shown in the low state).

(72) In the example illustrated in FIG. 3, the shutdown control CA is received by the arbitration module MA before emitting an access request RA to the memory by the contactless reader LSC.

(73) The access request RA is transmitted in a frame comprising a first start-of-frame bit S, the access request RA then a last end-of-frame bit E. The shutdown control CA is transmitted in a frame comprising a first start-of-frame bit S, the shutdown control CA then an acknowledgement bit A followed by an end-of-frame bit P.

(74) No write access is therefore in progress at the end of the reception of the shutdown control AC, as shown by the low state of signal 102.

(75) Since no write access to the memory is in progress, the arbitration module MA can directly shut down the contactless interface IR. Signal 103 thus switches to the low state. After shutting down the contactless interface IR, the arbitration module MA generates an interrupt signal which it transmits to the wired interface IF (see signal 104 switching to the low state).

(76) With the contactless interface IR shut down, the access request of the contactless reader LSC is not processed. No response is therefore sent following this access request (the absence of response being represented by the piece of information NREP). The master module MM then obtains exclusive access of the transponder TRS to the memory MEM.

(77) In the example illustrated in FIG. 4, the shutdown control CA is received by the arbitration module MA while an access request RA emitted by the contactless reader LSC is also received by the arbitration module MA.

(78) As previously, the access request RA is transmitted in a frame comprising a first start-of-frame bit S, the access request RA then a last end-of-frame bit E. The shutdown control CA is transmitted in a frame comprising a first start-of-frame bit S, the shutdown control CA and an acknowledgement bit A followed by an end-of-frame bit P.

(79) The reception of the shutdown control ends before the end of the reception of the access request. No write access is therefore in progress at the end of the reception of the shutdown control, as shown by the low state of signal 102.

(80) Since no write access to the memory is in progress, the arbitration module MA can directly shut down the contactless interface IR. The signal 103 thus switches to the low state.

(81) After shutting down the contactless interface IR, the arbitration module MA generates an interrupt signal which it transmits to the wired interface IF (see signal 104 switching to the low state).

(82) With the contactless interface IR shut down, the access request emitted by the contactless reader LSC is not processed. No response is therefore sent following this access request (the absence of response being represented by the piece of information NREP). The master module MM then obtains exclusive access of the transponder TRS to the memory MEM.

(83) In the example illustrated in FIG. 5, the shutdown control CA is received by the arbitration module MA after a memory access request NWM from the contactless reader LSC has been received, but before a response to this access control has been emitted by the transponder TRS. Here, this access request NWM is not a memory write access request.

(84) The access request NWM is transmitted in a frame comprising a first start-of-frame bit S, the access request NWM then a last end-of-frame bit E. The shutdown control CA is transmitted in a frame comprising a first start-of-frame bit S, the shutdown control CA then an acknowledgement bit A followed by an end-of-frame bit P.

(85) Since no write access to the memory is in progress, the arbitration module MA can directly shut down the contactless interface IR. The signal 103 thus switches to the low state.

(86) After shutting down the contactless interface IR, the arbitration module MA generates an interrupt signal which it transmits to the wired interface IF (see signal 104 switching to the low state).

(87) With the contactless interface IR shut down, the access request from the contactless reader LSC is not processed. No response is sent following this access request (the absence of response being represented by the piece of information NREP). The master module MM then obtains exclusive access of the transponder TRS to the memory MEM.

(88) In the example illustrated in FIG. 6, the shutdown control CA is received by the arbitration module MA after a request for write access WM to the memory from the contactless reader LSC has been received, but before a response to this access control has been emitted by the transponder TRS.

(89) The write access WM request is transmitted in a frame comprising a first start-of-frame bit S, the access request WM then a last end-of-frame bit E. The shutdown control CA is transmitted in a frame comprising a first start-of-frame bit S, the shutdown control CA then an acknowledgement bit A followed by an end-of-frame bit P.

(90) Because a write memory access is in progress, the arbitration module MA cannot directly shut down the contactless interface IR to prevent memory corruption that may result from shutting down the contactless interface IR during write access to the memory by this contactless interface IR.

(91) The arbitration module MA therefore waits for the write access to complete before shutting down the contactless interface IR. After write access is complete, the arbitration module MA shuts down the contactless interface IR. The signal 103 thus switches to the low state.

(92) After shutting down the contactless interface IR, the arbitration module MA generates an interrupt signal which it transmits to the wired interface IF (see signal 104 switching to the low state).

(93) With the contactless interface IR shut down, no response is sent following this access request (the lack of response being represented by the piece of information NREP). The master module MM then obtains exclusive access of the transponder TRS to the memory MEM.

(94) In the example illustrated in FIG. 7, the contactless reader LSC emits a memory access request. This memory access request is processed and a response REP to this access request is transmitted to the contactless reader LSC.

(95) The access request RA is transmitted in a frame comprising a first start-of-frame bit S, the access request RA then a last end-of-frame bit E. The response REP is contained in a frame starting with a start-of-frame bit S. The shutdown control CA is transmitted in a frame comprising a first start-of-frame bit S, the shutdown control CA then an acknowledgement bit A followed by an end-of-frame P bit.

(96) The shutdown control is received after the start of transmission to the contactless reader LSC of the response but before the end of this transmission. Since no write access to the memory occurs after receiving the shutdown control, the arbitration module MA can directly shut down the contactless interface IR. Signal 103 thus switches to the low state.

(97) After shutting down the contactless interface IR, the arbitration module MA generates an interrupt signal which it transmits to the wired interface IF (see signal 104 switching to the low state).

(98) With the contactless interface IR shut down, the access request emitted by the contactless reader LSC is not processed and the transmission of the response REP is not finalized. The master module MM then obtains exclusive access of the transponder TRS to the memory MEM.

(99) The system SYS as described above can be used in the field of connected objects. As such, FIG. 8 schematically illustrates a connected object OBJ comprising a system SYS as described above. The connected object OBJ can be a connected watch, or a connected home automation equipment, or else a connected public equipment, such as a connected lamppost, without these examples being limiting.