ONE-TIME PROGRAMMABLE MEMORY CONTROLLER, RELATED PROCESSING SYSTEM, INTEGRATED CIRCUIT AND METHOD

Abstract

In an embodiment a One-Time Programmable (OTP) memory controller includes a data register, a given number K of shadow-registers, wherein the number K is smaller than a given number N of memory slots of an OTP memory area, a communication interface configured to receive a read request requesting the data of a given memory slot and a control circuit configured to receive a preload start signal and a shadow-register preload enable signal, wherein the control circuit is configured to manage a preload phase and a data-read phase.

Claims

1. A One-Time Programmable (OTP) memory controller comprising: a data register; a given number K of shadow-registers, wherein the number K is smaller than a given number N of memory slots of an OTP memory area; a communication interface configured to receive a read request requesting the data of a given memory slot; and a control circuit configured to receive a preload start signal and a shadow-register preload enable signal, wherein the control circuit is configured to manage a preload phase and a data-read phase, wherein, in response to the preload start signal, the control circuit is configured to perform the preload phase by: determining a mapping between the given number K of shadow-registers and the given number N of memory slots, determining, for each of the shadow-registers, whether the respective shadow-register is preloadable as a function of the shadow-register preload enable signal, in response to determining that a shadow-register is preloadable, transferring data from the memory slot mapped to the shadow-register to the respective shadow-register, and once the shadow-register is preloaded based on the shadow-register preload enable signal, asserting a preload end signal and start the data-read phase, and wherein the control circuit is configured to perform the data-read phase by: selecting the respective memory location indicated in the read request, determining whether the selected memory location is mapped to a shadow register, in response to determining that the selected memory location is mapped to the shadow register, selecting the shadow-register mapped to the selected memory location and determining whether the selected shadow-register has been pre-loaded, in response to determining that the selected shadow-register has been pre-loaded, transmitting the data stored to the selected shadow register via the communication interface, in response to determining that the selected shadow-register has not been pre-loaded, transferring data from a selected memory slot to the selected shadow-register and then transmit the data stored to the selected shadow register via the communication interface, and in response to determining that the selected memory location is not mapped to a shadow register, transferring data from the selected memory slot to the data register and then transmit the data stored to the data register via the communication interface.

2. The OTP memory controller according to claim 1, wherein the control circuit is configured to: receive a shadow-register mapping signal; and determine the mapping between the given number K of shadow-registers and the given number N of memory slots as a function of the shadow-register mapping signal.

3. The OTP memory controller according to claim 1, wherein the shadow-register preload enable signal comprises the given number N of bits, and wherein each bit indicates whether a respective memory slot is preloadable.

4. The OTP memory controller according to claim 1, wherein the shadow-register preload enable signal comprises the given number K of bits, and wherein each bit indicates whether a respective shadow-registers is preloadable.

5. The OTP memory controller according claim 1, wherein the control circuit is configured to perform a data-write phase by: receiving a write request via the communication interface and selecting the respective memory location indicated in the write request, wherein the write request comprises respective data to be stored to the selected memory location; determining whether the selected memory location is mapped to a shadow register; in response to determining that the selected memory location is mapped to a shadow register, selecting the shadow-register mapped to the selected memory location, storing the data to be stored to the selected shadow-register and programming the data stored to the selected shadow-register to the selected memory location; and in response to determining that the selected memory location is not mapped to a shadow register, storing the data to be stored to the data register and programming the data stored to the data register to the selected memory location.

6. A processing system comprising: a power supply circuit configured to receive an input voltage and provide a first supply voltage and a second supply voltage, wherein the power supply circuit is configured to selectively enable the first supply voltage when a low-power control signal is de-asserted and disable the first supply voltage when the low-power control signal is asserted; a first sub-circuit configured to receive the first supply voltage, wherein the first sub-circuit comprises: the OTP memory area comprising the given number N of memory slots; and the OTP memory controller according to claim 1, wherein the OTP memory controller is configured to manage the OTP memory area; and a second sub-circuit configured to receive the second supply voltage.

7. The processing system according to claim 6, further comprising a power supply monitoring circuit configured to assert the preload start signal when the first supply voltage exceeds a given threshold voltage.

8. The processing system according to claim 7, further comprising: a digital processing circuit; a first resource connected to the digital processing circuit and configured to receive first configuration data; and a reset management circuit configured to, in response to the preload end signal, start the digital processing circuit.

9. The processing system according to claim 8, wherein the second sub-circuit comprises: a power management circuit configured to generate the low-power control signal, and a second resource connected to the digital processing circuit and configured to receive second configuration data.

10. The processing system according to claim 9, wherein the power management circuit is configured to: in response to a request received from the digital processing circuit, assert the low-power control signal, and in response to an event signal, de-assert the low-power control signal.

11. The processing system according to claim 6, wherein the OTP memory controller is configured to map a first memory slot of the OTP memory storing first configuration data to a first shadow-register and a second memory slot of the OTP memory storing second configuration data to a second shadow-register.

12. The processing system according to claim 6, wherein the processing system is configured to: in response to switching-on the processing system, assert the preload start signal via the power supply monitoring circuit and set the preload enable signal in order to preload first configuration data from a first memory slot to a first shadow-register and second configuration data from a second memory slot to a second shadow-register and, in response to the preload end signal, transfer the first configuration data from the first shadow-register to a first resource and the second configuration data from the second shadow-register to the second resource; send via a digital processing circuit a request to a power management circuit in order to assert the low-power control signal thereby disabling the first supply voltage and switching off the first sub-circuit; in response to an event signal, de-assert the low-power control signal via the power management circuit thereby enabling the first supply voltage and switching on the first sub-circuit; and in response to switching on the first sub-circuit, assert the preload start signal via the power supply monitoring circuit and set the preload enable signal in order to preload the first configuration data from the first memory slot to the first shadow-register and disable the preloading of the second configuration data from the second memory slot to the second shadow-register and, in response to the preload end signal, transfer the first configuration data from the first shadow-register to the first resource and inhibit the transfer of the second configuration data from the second shadow-register to the second resource.

13. The processing system according to claim 6, wherein the processing system is configured to set the shadow-register mapping signal in order to map a first memory slot of the OTP memory storing first configuration data to a first shadow-register and a second memory slot of the OTP memory storing second configuration data to a second shadow-register.

14. The processing system according to claim 6, further comprising a circuit configured to generate the preload enable signal.

15. The processing system according to claim 14, wherein the circuit is configured to generate the preload enable signal as a function of at least one of: a first signal received from a first resource, wherein the first signal indicates whether the first resource has stored first configuration data; a second signal received from a second resource, wherein the second signal indicates whether the second resource has stored second configuration data; a third signal received from a configuration circuit configured to transfer first configuration data from a first shadow-register to the first resource and the second configuration data from a second shadow-register to the second resource, wherein the third signal indicates whether the first configuration data have been transferred from the first shadow-register to the first resource and/or whether the second configuration data have been transferred from the second shadow-register to the second resource; or a fourth signal received from a digital processing circuit, wherein the fourth signal indicates whether to pre-load the first configuration data and/or whether to pre-load the second configuration data.

16. The processing system according to claim 14 wherein the second sub-circuit comprises the circuit.

17. A method for operating a processing system, the method comprising: switching-on the processing system; in response to switching-on the processing system, asserting, by a power supply monitoring circuit of the processing system, a preload start signal and setting a preload enable signal in order to preload first configuration data from a first memory slot to a first shadow-register and second configuration data from a second memory slot to a second shadow-register; in response to a preload end signal, transferring the first configuration data from the first shadow-register to a first resource and the second configuration data from the second shadow-register to a second resource; sending, by a digital processing circuit of the processing system, a request to a power management circuit in order to assert a low-power control signal thereby disabling a first supply voltage and switching-off a first sub-circuit; in response to an event signal, de-asserting, by the power management circuit, the low-power control signal thereby enabling the first supply voltage and switching-on the first sub-circuit; and in response to switching-on the first sub-circuit, asserting the preload start signal via the power supply monitoring circuit and setting the preload enable signal in order to preload the first configuration data from the first memory slot to the first shadow-register and disable the preloading of the second configuration data from the second memory slot to the second shadow-register and, in response to the preload end signal, transferring the first configuration data from the first shadow-register to the first resource and inhibiting the transfer of the second configuration data from the second shadow-register to the second resource.

18. A One-Time Programmable (OTP) memory controller comprising: a data register; a given number K of shadow-registers, wherein the number K is smaller than a given number N of memory slots of an OTP memory area; a communication interface configured to receive a read request requesting the data of a given memory slot; and a control circuit configured to receive a preload start signal and a shadow-register preload enable signal, wherein the control circuit is configured to manage a preload phase and a data-read phase, wherein, in response to the preload start signal, the control circuit is configured to perform the preload phase by: determining a mapping between the given number K of shadow-registers and the given number N of memory slots, determining, for each of the shadow-registers, whether the respective shadow-register is preloadable as a function of the shadow-register preload enable signal, in response to determining that a shadow-register is preloadable, transferring data from the memory slot mapped to the shadow-register to the respective shadow-register, and once the shadow-register is preloaded based on the shadow-register preload enable signal, asserting a preload end signal and start the data-read phase.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Embodiments of the present disclosure will now be described with reference to the annexed drawings, which are provided purely by way of non-limiting example and in which:

[0061] FIG. 1 shows an example of an electronic system;

[0062] FIG. 2 shows an example of a processing system;

[0063] FIG. 3 shows an example of an OTP memory;

[0064] FIG. 4 shows an embodiment of a processing system;

[0065] FIG. 5 shows an embodiment of the operation of the processing system of FIG. 4;

[0066] FIG. 6 shows an embodiment of an OTP memory according to the present disclosure;

[0067] FIGS. 7-10 show embodiments of the operation of the OTP memory of FIG. 6; and

[0068] FIG. 11 shows an embodiment of a processing system according to the present disclosure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0069] In the following description, numerous specific details are given to provide a thorough understanding of embodiments. The embodiments can be practiced without one or several specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments.

[0070] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0071] The headings provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0072] In the following FIGS. 4 to 11 parts, elements or components which have already been described with reference to FIGS. 1 to 3 are denoted by the same references previously used in such Figure; the description of such previously described elements will not be repeated in the following in order not to overburden the present detailed description.

[0073] As mentioned before, various embodiments of the present disclosure provide solutions for managing an OTP memory. Reference can be made to the previous description of FIGS. 1 to 3 for a general description of an OTP memory and a processing system comprising such an OTP memory.

[0074] FIG. 4 shows an embodiment of a processing system 10a according to the present disclosure.

[0075] As mentioned before, the present disclosure relates specifically to processing system 10a adapted to be switched off at least in part. For example, for this purpose, the processing system 10a comprise typically two sub-circuits: [0076] a first sub-circuit 32.sub.1 comprising circuits to be switched off; and [0077] a second sub-circuit 32.sub.2 comprising circuits, which are maintained enabled/switched-on, so called always-on domain.

[0078] In the embodiment considered, the processing system 10a comprises thus a power supply circuit 117 configured to generate a first supply voltages VDD.sub.1 for the first sub-circuit 32.sub.1 and a second supply voltages VDD.sub.2 for the first sub-circuit 32.sub.2. For example, for this purpose the power supply circuit 117 may receive an input voltage Vin, such as a voltage provided by a battery. Specifically, once the supply voltage Vin is received, the power supply circuit 117 generates the supply voltage VDD.sub.2. For example, the voltage VDD.sub.2 may correspond to the voltage Vin. However, the power supply circuit 117 may also comprise a voltage source, such as an electronic converter, configured to generate a regulated voltage VDD.sub.2 based on the input voltage Vin. Moreover, the power supply circuit 117 is configured to generate the voltage VDD.sub.1. However, in this case, the power supply circuit 117 is configured to provide the voltage VDD.sub.1 only when a signal POFF has a given logic level/is de-asserted, e.g., when the signal POFF is set to low. For example, in the simplest case, the voltage VDD.sub.1 may be provided via an electronic switch, which is connected to the voltage VDD.sub.2 and closed when the signal POFF has the given logic level/is de-asserted. In general, the voltages VDD.sub.1 and VDD.sub.2 may have the same value or different values, e.g., the value of voltage VDD.sub.2 may be smaller than the value of the voltage VDD.sub.1.

[0079] For example, in the embodiment considered, the first sub-circuit 32.sub.1 comprises a processing core 102a, one or more resources 106.sub.1, an OTP memory 120a and a hardware configuration circuit 108a. For a more detailed description of the connection between these circuits may be made reference to the description of FIGS. 2 and 3. In this respect, the communication system 114/114b and/or the memory controller(s) 100 may be included in the sub-circuit 32.sub.1 or the sub-circuit 32.sub.2.

[0080] Specifically, in the embodiment considered, the first sub-circuit 32.sub.1 comprises also a power supply monitoring circuit 115 configured to assert a signal POK when the supply voltage VDD.sub.1 exceeds a given threshold value, i.e., when the first sub-circuit 32.sub.1 is supplied. In response to this signal POK, the OTP memory 120a preloads the shadow-registers 1208 of the OTP memory 120a and once having preloaded the shadow-registers 1208, the OTP memory 120a asserts the signal OTP_DONE (see also the description of FIG. 3).

[0081] In the embodiment considered, the signals POK and OTP_DONE are provided to a reset management circuit 116. Specifically, in the embodiment considered, the reset management circuit 116 is configured to: [0082] in response to the signal POK, start a reset phase by asserting a reset signal RST provided to the processing core 102a and possibly one or more further reset signals used to reset the registers of one or more of other circuits of the first sub-circuit 32.sub.1, such as one or more resources/peripherals 106.sub.1; [0083] in response to the signal OTP_DONE, start a configuration phase by asserting a signal SCFG, wherein the hardware configuration circuit 108a reads, in response to the signal SCFG, one or more data from the OTP memory 120; and [0084] once the hardware configuration circuit 108a has read the data from the OTP memory 120, e.g., in response to a signal ECFG provided by the hardware configuration circuit 108 (not shown in FIG. 4), start a software run-time phase by de-asserting the reset signal RST provided to the processing core 102a.

[0085] Accordingly, in order to implement a low-power mode, the second sub-circuit 32.sub.2 may comprise a power management circuit 118. Specifically, in the embodiment considered, the power management circuit 118 is configured to assert the signal POFF in response to a request received from the first sub-circuit 32.sub.1, for example a request received from the processing core 102a. For example, for this purpose, the power management circuit 118 may be connected to the communication channel 114 or 114b, whereby the processing core 102a may request a switch-off by sending via software instructions a (write) request to the power management circuit 118. Accordingly, once having received the request, and the signal POFF is asserted, the power supply circuit 117 disables/switches off the voltage VDD.sub.1 of the first sub-circuit 321, thereby switching off the respective circuits.

[0086] Conversely, in order to de-assert the signal POFF, the power management circuit 118 may monitor one or more signals indicating given events, such as one or more trigger signals, e.g.: [0087] a first trigger/event signal TRIG1 received via a terminal of the processing system 10a, such as a pin or pad of a respective integrated circuit; and/or [0088] a second trigger/event signal TRIG2 provided by a resource/peripheral in the sub-circuit 32.sub.2, such as a timer circuit, such as a watchdog timer, a communication interface, an analog comparator, etc.

[0089] Accordingly, in various embodiments, each resource/peripheral 106 of the processing system 10a may be either in the sub-circuit 32.sub.1 or the sub-circuit 32.sub.2. In various embodiments, the processing system 10a may be configured to permit for one or more of the resources/peripherals 106 a selection whether the respective resource/peripheral 106 belongs to the first sub-circuit 32.sub.1 (and are thus switched off) or to the second sub-circuit 32.sub.2 (and may thus be used to generate the trigger signal TRIG2).

[0090] Accordingly, in response to the event/trigger signal TRIG1 and/or TRIG2, the power management circuit 118 de-asserts the signal POFF, whereby the power-supply circuit 117 switches on again the supply voltage VDD.sub.1, whereby the first sub-circuit 32.sub.1 is started again, thereby preloading the data to the shadow-registers 1208 and executing the reset, configuration and software runtime phase.

[0091] Accordingly, as shown in FIG. 5, once the processing system 10a (i.e., both sub-circuits 32.sub.1 and 32.sub.2) is switched on, the OTP memory 120a asserts the signal OTP_DONE only after a time T.sub.R used to preload the shadow-registers 1208. Once the power management circuit 118 asserts then the signal POFF, the first sub-circuit 32.sub.1 is switched off. However, when de-asserting the signal POFF (in response to an event), the power supply monitoring circuit 115 asserts again the signal POK, and the OTP memory 120 asserts the signal OTP_DONE again only after a time T.sub.R used to preload the shadow-registers 1208. This operation is thus repeated for each switch-on operation of the first sub-circuit 32.sub.1.

[0092] However, as shown in FIG. 4, indeed the hardware configuration circuit 108a may provide a first set of configuration data CD.sub.1 to circuits within the first sub-circuit 321, such as one or more resources 106.sub.1. Moreover, the hardware configuration circuit 108a may provide a second set of configuration data CD.sub.2 to circuits within the second sub-circuit 32.sub.2, such as one or more resources 106.sub.2. However, the second sub-circuit 32.sub.2 is not switched off, whereby the respective circuits do not lose the configuration data CD.sub.2. Moreover, also the circuits within the first sub-circuit 32.sub.1 may not use always all configuration data, e.g., in case the cryptographic co-processor is not used.

[0093] Accordingly, in various embodiments, the OTP memory 120a permits to specify which data should be preloaded, in response to the signal POK, from the OTP memory areas 1200 to the shadow-registers 1208.

[0094] FIG. 6 shows an embodiment of an OTP memory 120a according to the present disclosure.

[0095] In the embodiment considered, the OTP memory 120a comprises: [0096] a memory area 1200 having a given number N of memory slots, i.e, slots OTP1, . . . , OTPN; [0097] a given number of K shadow-registers SREG, i.e, registers SREG1, . . . , SREGK, wherein the number K is smaller than the number N; [0098] a (shared) register 1206; [0099] a communication interface 1202, such as a communication interface for connecting the OTP memory 120a to the peripheral bus 114b; [0100] a control circuit 1204a.

[0101] In various embodiments, the OTP memory 120a may also comprise the optional interfaces 1210 and/or 1212.

[0102] Specifically, as schematically shown in FIGS. 6, each memory slot of the OTP memory area 1200 has a given number M of bits, e.g., implemented with respective fuses or similar one-time programmable storage elements. Conversely, each shadow-register SREG (a similarly the register 1206) has a given number P of bits. Generally, the number P may correspond to the number M, i.e., all bits of a given OTP memory slot are transferred to the respective shadow-register SREG, or the number P may be smaller than the number M. For example, the latter solution is usually preferably, because the bits stored to a given memory slot of the memory area 1200 may comprise additional error detection and optionally correction data. For example, the data may be stored in a redundant manner to memory area 1200. For example, each bit of a given data word may be stored a plurality of times to the respective memory slot. For example, 32 bits of data may indeed be stored to a memory slot having 128 bits, wherein each bit is stored to four respective OTP storage elements. However, also more complex error-correction codes (ECC) may be used, wherein one or more ECC bits are added to the data, or the data are stored in an encoded form. Accordingly, in various embodiments, the control circuit 1204a may be configured to transfer data from a given memory slot to a shadow-register SREG (or similarly the shared register 1206) by: [0103] reading the M bits from the memory slot, [0104] extracting P bits of data from the M bits read from the memory slot, e.g., by using an error correction code or decoding the M bits, and [0105] storing the extracted P bits (corresponding to the actual data) to a respective shadow-register SREG (or the shared register 1206).

[0106] Accordingly, in case the control circuit 1204a is also configured to write data to the OTP memory area 1200, e.g., by storing via the communication interface 1202 (or another communication interface of the OTP memory 120a) respective data to a shadow-register SREG or the shared register 1206, the control circuit may be configured to transfer the respective data to a given memory slot by: [0107] reading the P bits from the register, [0108] generating M bits by encoding the P bits of data or adding ECC bits to the P bits; and [0109] storing the P bits to the respective memory slot.

[0110] For example, when each bit of the P bits of data should be programmable individually (bit-programmable), the M bits comprise preferably redundant bits for each of the P bits, such as at least two further redundant bits. Conversely, in case only the complete word may be written (word programmable), also other ECC schemes may be used.

[0111] In addition to managing the read and write requests received via the interface(s) of the OTP memory 120a, the control circuit 1204a also manages a preload mechanism. Specifically, in the embodiment considered, the OTP memory 120a, and in particular the control circuit 1204a of the OTP memory 120a, receives for this purpose the signal POK and a shadow-register selection signal SSA.

[0112] Specifically, in the embodiment considered, the signal SSA indicates the mapping of the K shadow-registers SREG to the N memory slots of the memory area 1200.

[0113] For example, FIG. 7 shows an embodiment, wherein the signal SSA has N bits, wherein each bit is associated univocally with a given memory slot and indicates whether the data of the respective memory slot should be transferred to a respective shadow-register.

[0114] For example, in FIG. 7 are shown twelve memory slots OTP1, . . . , OTP12 and five shadow-registers SREG1, . . . , SREG5. For example, in this case, the bit sequence 00101001010 may indicate that the memory slots OTP2, OTP4, OTP5, OTP8 and OTP10 should be transferred. For example, in various embodiments, the shadow-registers SREG are assigned sequentially to the selected memory slots, i.e., the control circuit 1204a may select the following assignment: [0115] the shadow-register REG1 is associated with the memory slot OTP2, [0116] the shadow-register REG2 is associated with the memory slot OTP4, [0117] the shadow-register REG3 is associated with the memory slot OTP5, [0118] the shadow-register REG4 is associated with the memory slot OTP8, and [0119] the shadow-register REG5 is associated with the memory slot OTP10.

[0120] Accordingly, in the embodiment considered, up to 5 bits may be asserted of the signal SSA.

[0121] In the embodiment considered, the control circuit 1204a may thus use the signal SSA in order to determine the mapping between memory slots and the shadow-registers. For example, when receiving a read request requesting the data stored to a given memory slot, the control circuit 1204a may use the signal SSA in order to determine whether the data of the respective slot are also stored to a shadow-register and: [0122] when the signal SSA indicates that the data of the respective slot are also stored to a shadow-register, transmit the data stored to the shadow-register, i.e., without performing a further read operation to the memory area 1200; and [0123] when the signal SSA indicates that the data of the respective slot are not stored to a shadow-register, transfer the data of the memory slot to the shared register 1206 and then transmit the data stored to the shared register 1206.

[0124] Accordingly, in the embodiment considered, the duration of the preload phase may be reduced, by enabling via the signal SSA only the preloading of data, which are also expected to be used by the processing system 10a during the next operation interval when the sub-circuit 32.sub.1 is switched on.

[0125] However, the inventors have observed that the use of the signal SSA alone may have several disadvantages. For example, on the one hand, this implies that given memory slots, which are not required for the boot of the processing system 10a may be read later on and even several times, whereby access times are significantly increased, because the data of the respective memory slot are not stored to a respective shadow-register.

[0126] Moreover, as mentioned before, the location of given data in the shadow-registers should also be fixed, e.g., because the OTP memory 120a may also provide the data of one or more of the shadow-registers directly. For example, a shadow-register may be arranged to store the MAC address of an Ethernet communication interface 106, whereby this shadow-register is directly connected to the Ethernet communication interface 106. In this context, the signal SSA may also be a static signal prior to the synthesis operation of the control circuit 1204a, whereby the respective combination logic circuit may be implemented in an optimized manner via the logic synthesis operation.

[0127] Accordingly, in various embodiments, the shadow-register selection signal SSA is used as a static signal, and is thus also identified as static shadow array signal. For example, based on the application, this signal may be hardwired within the processing system 10a or may be a static signal prior to the logic synthesis operation, thereby specifying permanently a given mapping of the shadow-registers 1208 to the memory area 1200. Conversely, the OTP memory 120a, in particular the control circuit 1204a, is configured to receive a further signal DSA specifying, which of the shadow-registers 1208 should be preloaded in response to the signal POK, i.e., the signal DSA specifies dynamically the preloading of the shadow-registers and is also identified as dynamic shadow array signal.

[0128] For example, FIG. 8 shows an embodiment, wherein the signal DSA has N bits, wherein each bit is associated univocally with a given memory slot and indicates whether the data transfer of the respective memory slot to the respective shadow-register (as indicated by the signal SSA) is enabled.

[0129] For example, for the exemplary situation shown in FIG. 8, the bit sequence 001010011010 of the signal SSA may again indicate that the memory slots OTP2, OTP4, OTP5, OTP8 and OTP10 are mapped to respective shadow-registers SREG1-SREG5. Moreover, the bit sequence 001000010010 of the signal DSA indicates that indeed only the memory slots OTP2, OTP5 and OTP10 should be preloaded. Accordingly, in the embodiment considered, while the shadow-registers SREG2 and SREG4 are mapped (via the signal SSA) to the memory slots OTP4 and OTP8, respectively, the control circuit 1204a does not preload these shadow-registers, butif requiredthe control circuit 1204a may load these shadow-registers only once a read request to the respective memory slot (OTP4 or OTP8) is received.

[0130] Conversely, FIG. 9 shows an embodiment, wherein the signal DSA has K bits, wherein each bit is associated univocally with a given shadow-register SREG and indicates whether the data transfer of the respective memory slot to the respective shadow-register (as indicated by the signal SSA) is enabled.

[0131] For example, for the exemplary situation shown in FIG. 8, the bit sequence 001010011010 of the signal SSA may again indicate that the memory slots OTP2, OTP4, OTP5, OTP8 and OTP10 are mapped to respective shadow-registers SREG1-SREG5. Moreover, the bit sequence 10101 of the signal DSA indicates that indeed only the shadow-registers SREG1, SREG3 and SREG5 should be preloaded based on the data stored to the memory slots OTP2, OTP5 and OTP10 (as indicated via the signal SSA). Accordingly, also in this case, the shadow-registers SREG2 and SREG4 are mapped (via the signal SSA) to the memory slots OTP4 and OTP8, respectively, and the control circuit 1204a does not preload these shadow-registers, butif requiredthe control circuit 1204a may load these shadow-registers only once a read request to the respective memory slot (OTP4 or OTP8) is received.

[0132] Accordingly, as shown in FIG. 10, once the processing system 10a (i.e., both sub-circuits 32.sub.1 and 32.sub.2) is switched on, the OTP memory 120a asserts the signal OTP_DONE after a time T.sub.R1 used to preload the shadow-registers 1208, which depends on the number of shadow-registers 1208, which are preloaded. For example, once the processing system is switched on, the signal DSA may correspond to the signal SSA, whereby all shadow-registers 1208 are preloaded, and at least part of these data is transferred to the other circuits of the processing system 10a. Once the power management circuit 118 asserts then the signal POFF, the first sub-circuit is switched off. When de-asserting the signal POFF (in response to an event), the power supply monitoring circuit 115 asserts again the signal POK. However, this time, the signal DSA may have less bits asserted, whereby less data are preloaded and the OTP memory 120 asserts the signal OTP_DONE after a time T.sub.R2 used to preload less shadow-registers 1208.

[0133] FIG. 11 shows in this respect an embodiment of a processing system 10a configured to generate the signals SSA and DSA.

[0134] Specifically, as mentioned before, the signal SSA may be hardwired or may just be a static signal used for the logic synthesis operation, e.g., in the context of a VHDL or Verilog model. Alternatively, in various embodiments, the signal SSA may be determined as a function of the data stored to a non-volatile memory. For example, in various embodiments, the control circuit 1204a is configured to determine the signal SSA based on the content of one or more memory slots of the OTP memory area 1200.

[0135] Conversely, in the embodiment considered, the signal DSA is provided by a circuit 122.

[0136] Specifically, as mentioned before, the data stored to the shadow-registers of the OTP memory 120a may be read by a processing core 102a and/or the hardware configuration circuit 108a.

[0137] For example, as schematically shown in FIG. 11, the hardware configuration circuit 108a may transfer configuration data CD.sub.1 to one or more resources 106.sub.1 in the sub-circuit 32.sub.1 and configuration data CD.sub.2 to one or more resources 106.sub.2 in the sub-circuit 32.sub.2. In this case, it may be useless to re-transmit the configuration data CD.sub.2 to the resources 106.sub.2 when just the sub-circuit 32.sub.1 is switched off.

[0138] Accordingly, in various embodiments, the circuit 122 may comprise for one or more bits of the signal DSA a respective register (or a respective set of redundant registers), and the hardware configuration circuit 108a may be configured to de-assert the bits associated with the configuration data CD.sub.2, whereby the respective memory slots of the OTP memory 120a are not preloaded at the next re-activation of the sub-circuit 32.sub.1. Conversely, when the complete processing system is switched off, also the registers of the circuit 122 will lose the stored data, whereby the signal DSA is reset. For example, in various embodiments, the circuit 122 is configured to provide, once having been reset, as signal DSA the same bit sequence as the signal SSA. For example, for this purpose, the signal SSA may also be provided to the circuit 122.

[0139] Similarly, the processing core 102a may be configured to program one or more of the registers of the circuit 122 in order to set the signal DSA. For example, for this purpose, the circuit 122 may be connected to the communication system 114, e.g., via the communication system 114b.

[0140] Additionally or alternatively, as schematically shown in FIG. 11, in various embodiments, the circuit 122 may be configured to determine at least part of the logic levels of bits of the signal DSA as a function of signals received from one or more of the resources 106, in particular the resources 106.sub.2. For example, one or more of the resources 106 may be configured to provide a signal indicating whether the respective resource has still stored to respective configuration data. Accordingly, in this case, one the sub-circuit 32.sub.1 is re-activated, a resource 106.sub.2 may indicate that it still has valid configuration data, while a resource 106.sub.1 may indicate that it does not have valid configuration data.

[0141] Generally, the above solutions may also be combined. For example, as schematically shown in FIG. 11, the circuit 122 may be configured to assert or de-assert a respective flag PL based on a signal provided by a resource 106 or programmed via the configuration circuit 108a, wherein this signal indicates that the respective configuration data are valid or invalid. Conversely, the processing core 102a may be configured to program a flag PE used to indicate whether the preload mechanical for the respective configuration data is enabled or disabled. Accordingly, in this case, the circuit 122 may be configured to: [0142] assert the respective bit of the signal DSA when the flag PL indicates that the respective configuration data are invalid and the flag PE indicates that preload mechanical for the respective configuration data is enabled; and [0143] de-assert the respective bit of the signal DSA when the flag PL indicates that the respective configuration data are valid or the flag PE indicates that preload mechanical for the respective configuration data is disabled.

[0144] For example, in this way, when the processing system 10a is switched on, the signal SSA may indicate that the memory slot comprising a MAC address should be preloaded to a given shadow-register 1208. Accordingly, in response to the signal POK, the control circuit 1204a uses the signals SSA and DSA to preload the shadow-registers. Specifically, due to the fact that the signal DSA has its reset value, the control circuit 1204a preloads the MAC address from the memory area 1200 to the respective shadow-register 1208. Once having finished the preloading of the shadow-registers, the control circuit 1204a asserts the signal OTP_DONE.

[0145] In case the hardware configuration circuit 108a is provided/used, the reset management circuit 116 may then assert the signal SCFG. In response to this signal, the hardware configuration circuit 108a reads the MAC address from the OTP memory and transmits the MAC address to an Ethernet communication interface 106 within the sub-circuit 32.sub.2 of the processing system 10a. Moreover, the hardware configuration circuit 108a may program a respective flag in the circuit 122.

[0146] Alternatively, the shadow-register 1208 may also be connected directly to the Ethernet communication interface 106. In this case, the Ethernet communication interface 106 may directly signal to the circuit 122 that the MAC address is valid.

[0147] Accordingly, when the processing system 10a actives the low power mode, wherein the sub-circuit 32.sub.1 is switched off, the Ethernet communication interface 106 will maintain the MAC address. Accordingly, once the sub-circuit 32.sub.1 is switched on again, the signal SSA again indicates that the memory slot comprising a MAC address should be preloaded to the same shadow-register 1208. Accordingly, in response to the signal POK, the control circuit 1204a uses the signals SSA and DSA to preload the shadow-registers. Specifically, this time the bit associated with the memory slot containing the MAC address is de-asserted, whereby, the control circuit 1204a omits the preloading of the MAC address from the memory area 1200 to the respective shadow-register 1208. Once having finished the preloading of the shadow-registers, the control circuit 1204a asserts again the signal OTP_DONE.

[0148] In case the hardware configuration circuit 108a is provided/used, the reset management circuit 116 may then assert again the signal SCFG. As shown in FIG. 11, in this case, the signal DSA or another similar signal is also provided to the hardware configuration circuit 108a. In this way, in response to the signal POK, also the hardware configuration circuit 108a omits the reading of the MAC address from the OTP memory.

[0149] Alternatively, when the shadow-register 1208 is connected directly to the Ethernet communication interface 106, the Ethernet communication interface 106 may simply not request the data from the shadow-register because the MAC address is still valid.

[0150] Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to what has been described and illustrated herein purely by way of example, without thereby departing from the scope of the present invention, as defined by the ensuing claims. For example, while in the previous description a software programmable processing core comprising a micro-processor has been used, also any other digital processing core may be used.