Patent Application
20060249585
This invention concerns non-volatile memories and applications of non-volatile memories, especially in chip cards or non-volatile memory drives, typically in smart cards, multimedia cards, SD cards, USB drives, digital cameras and mobile phones.
Flash-memory cards are offered for many different applications. For every application, a certain number of write and read cycles is specified, which may be, for example, a minimum of 500,000 write/erase cycles per page for the 66P UCP chip card controllers or typically 100,000 write/erase cycles for flash memories. The specified number of cycles is guaranteed by the producer. Therefore, the memory chips must be tested and selected according to their quality and expected performance. The chips that do not reach the specified standard have to be rejected.
On the other hand, some applications are provided with flash-memory cards that could be used also in applications for which a much higher number of programming cycles are specified. In other applications the total number of write/read cycles is artificially reduced, for instance the so-called disposable digital cameras (single-use cameras), which can be used only once. Except for this special application, a user of a flash-memory card is not provided with any information about the maximum number of write/read cycles that are possible or of a remaining number of write/read cycles to be performed until the card is used up. Thus, the randomness of the actual number of possible write/read cycles of flash-memory cards is in the way of an optimal exploitation of this commodity.
In one aspect, the present invention provides a non-volatile memory that is better adapted to a special application with respect to the number of write/read cycles.
In a further aspect, the invention provides a non-volatile memory that is better adapted to the requirements of a commercial market.
In still a further aspect, the invention provides a non-volatile memory that is better suited to various applications, which require different levels of performance, especially chip cards and non-volatile memory drives.
The non-volatile memory according to the preferred embodiment of this invention makes use of a counter which counts the number of performed write/read cycles and which is arranged in or at the memory, preferably integrated in a semiconductor chip, either together with a controller circuit or in the memory. Storage capacity can preferably be provided in the memory to store a maximum number of write/read cycles as a reference, said maximum number depending on an estimated or evaluated performance of the memory. In preferred embodiments, the non-volatile memory can be a flash-memory that is programmed and erased by operating modes that are known per se.
Preferred embodiments also comprise circuitry adapted to display information about the status of the memory, e.g., either by displaying the number of write/read cycles already performed or by displaying a remaining number of write/read cycles according to a specified total number of cycles. To this purpose, a display can be integrated together with the memory on the same carrier, for instance on a chip card. The displays of devices such as mobile phones can also be used, if their standard function is enhanced accordingly. Also, displays of terminals or external devices such as chip card readers can be used to show the status of the memory.
Additional means may be provided to block a function of the memory after a specified number of write/read cycles. The number of cycles can be specified in advance according to the relevant commercial requirements, for instance depending on the price of the memory. The blocking mechanism is preferably realized by additional electronic circuits, which may be integrated in a controller circuitry of the memory.
Further means may be provided to restore a blocked function and to enable a further number of write/read cycles, for example after a payment of a fee for the further use of the memory. In this manner, the application of the memory can be adapted to the special requirements of the user. The memory can also be provided with a plurality of different levels of performance, which can be activated and adjusted to the customer's wishes. The additional operations may also be implemented, for example, in the controller circuitry. The inventive feature of the integrated counter offers a multitude of new applications.
It is of advantage for the customer, if he can buy flash-memory cards of different price levels depending on the number of write/read cycles which can be performed in the respective application. The revenues of the producers are increased, because the produced cards can be used according to their individual quality level, and the number of rejects are thus reduced. Programmable flash-memory cards can be offered with an explicit specification of a different number of write/read cycles according to the application. This is especially advantageous in the case of flash-memory cards like MMC, SD cards and USB drives.
The non-volatile memories according to the preferred embodiment of this invention can be provided by memory chips that have been selected or classified by cycling and data retention tests that are performed in the course of a standard production process. A storage of the expected maximum number of write/read cycles of the flash-memory chips that belong to a selection in the non-volatile memory may render a variety of memories of different specified quality or different specified levels of performance. The customer can choose according to his own requirements and demands and need not pay more than necessary for the memory which he chooses for his application.
The non-volatile memory according to embodiments of this invention can be used in conjunction with devices that are already integrated in controller circuits of memory chips and detect memory cells that are no longer usable or that are prone to degradation. Circuitry, such as a disturb counter, can be used to keep a record of the number of cycles already performed or of the remaining number of possible write/read cycles that can be displayed either on a display that is combined with the memory or on a display of a terminal or some other external device belonging to the application of the memory, for example an application in a flash-memory card. In this manner, the user is always informed of the state of his non-volatile memory and is able to check how long or how often the memory will be applicable.
Circuitry can be provided to restore or reactivate a memory which is initially provided with a number of write/read cycles that is smaller than the maximum possible number of cycles. After the payment of the corresponding fee, the memory is switched into an operating mode which provides a further specified number of write/read cycles, until the memory is definitely and finally used up.
If testing circuitry or an electronic circuit is provided to check the degradation of the memory cells or to estimate or evaluate the residual lifetime of the memory by the number of memory cells that have already been cancelled from a table of addresses, because they do no longer operate, a continuous update of the remaining number of write/read cycles is also possible. If the user is warned of a premature failure of the memory device by means of a suitable display, they can exchange the memory in time for a new copy. If the memory is provided with a blocking function, applications such as mobile phone or internet offer the possibility to activate the memory online on the customer's request. Thus the non-volatile memory according to the invention offers a plurality of new applications and an improved usage of new media, and enables an adaptation of the specified number of write/read cycles to a mercantile agreement.
These and other features and advantages of the invention will become apparent from the following brief description of the drawings, detailed description and appended claims and drawings.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
The following list of reference symbols can be used in conjunction with the figures.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
