Static information storage and retrieval – Floating gate – Particular biasing
Reexamination Certificate
2001-12-14
2004-10-19
Le, Vu A. (Department: 2824)
Static information storage and retrieval
Floating gate
Particular biasing
C365S230030
Reexamination Certificate
active
06807106
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a memory system for data storage and, more particularly, to a hybrid density memory system for data storage.
2. Description of the Related Art
Memory cards are commonly used to store digital data for use with various products (e.g., electronic products). Examples of memory cards are flash cards that use Flash type or EEPROM type memory cells to store the data. Flash cards have a relatively small form factor and have been used to store digital data for products such as cameras, hand-held computers, set-top boxes, hand-held or other small audio players/recorders (e.g., MP3 devices), and medical monitors. A major supplier of flash cards is SanDisk Corporation of Sunnyvale, Calif.
These memory cards are increasingly called on to store greater and greater amounts of data. Consequently, individual storage elements within these memory cards have been developed to support multiple levels so as to effectively store multiple bits of data. Traditional storage elements store only two states, while multiple level or high density storage elements store more than two states (e.g., four states). For example, individual storage elements in some of today's multiple-level memory cards can store four (4) levels and thus effectively enable a single storage element to act as two (2) bits of data. While these multiple levels allow a memory array to store substantially greater amounts of data without a corresponding increase in size or cost, it is more difficult to read stored data out of the memory array. As a result, performance (primarily, read performance) of the memory card is negatively impacted.
Thus, there is a need for improved approaches for providing high density storage while maintaining high performance operation of memory cards.
SUMMARY OF THE INVENTION
Broadly speaking, the invention relates to a memory system (e.g., memory card) offering hybrid density storage. The memory system yields both high density storage and high performance operation. According to one aspect of the invention, certain data to be stored in the memory system can be stored in lower density storage so that it provides robust storage and/or high speed retrieval. Other data, which can be retrieved at moderate speeds or moderate robustness, can be stored to higher density storage in a space (area) efficient manner.
The invention can be implemented in numerous ways. For example, the invention can be implemented as a system, device or method. Several embodiments of the invention are discussed below.
As a memory system that couples to a host, one embodiment of the invention includes at least a plurality of storage elements, a first portion of the storage elements being configured for low density storage, and a second portion of the storage elements being configured for high density storage; and a controller operatively connected to the storage elements, the controller operates to receive commands for data access from the host and to control reading and writing of data into the storage elements in accordance with the commands.
As a hybrid memory device having a single substrate, one embodiment of the invention includes at least a plurality of low density storage elements, a plurality of high density storage elements, and a controller operatively connected to the low density storage elements and the high density storage elements. The controller operates to control read, write and erasure of data into the low density storage elements and the high density storage elements.
As a portable memory card, one embodiment of the invention includes at least a data storage array, the data storage array including at least a first area of data storage having a first degree of robustness and a second area of data storage having a second degree of robustness; and a controller operatively connected to the storage elements, the controller operating to control reading and writing to the data storage array.
As a portable memory card, another embodiment of the invention includes at least a data storage array, the data storage array including at least a first area of data storage having a first density of data storage and a second area of data storage having a second density of data storage, the second density being at least twice that of the first density; and a controller operatively connected to the storage elements, the controller operates to control reading and writing to the data storage array.
As a method for rapidly forming an address translation table for a memory product having data storage elements arranged in logical blocks, each of the logical blocks including a plurality of data units, each of the data units having a header portion and a data portion, one embodiment of the invention includes at least the operations of: determining that the address translation table needs to be generated; reading the header portion of at least one of the data units within each of the logical blocks; determining physical addresses for each of the logical blocks from the corresponding header portion read; and forming the address translation table by saving the physical addresses in association with logical addresses for the logical blocks corresponding thereto.
Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
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Gonzales Carlos
Khalid Shahzad B.
Beyer Weaver & Thomas LLP
Le Vu A.
SanDisk Corporation
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