Synchronous page-mode phase-change memory with ECC and RAM cache
First Claim
1. A method for writing to a phase-change memory comprising:
- receiving from a host a burst write command including a host address and host data in a command buffer;
comparing a portion of the host address to a plurality of tags in a lookup table and for storing the host data in the lookup table when a tag in the plurality of tags matches the portion of the host address;
when the portion of the host address does not match any valid tag in the plurality of tags, allocating a new entry in the lookup table for the host address and storing the host data in the new entry;
copying the host data from the lookup table to the phase-change memory by storing a data word data as binary bits each represented by a chalcogenide glass layer having a melting point that is higher than a crystallization point, the chalcogenide glass layer forming a variable resistor that alters a sensing current when a binary bit is read; and
representing a first binary logic state using a crystalline state of the variable resistor and representing a second binary logic state using an amorphous state of the variable resistor for binary bits stored in the phase-change memory.
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Accused Products
Abstract
Phase-change memory (PCM) cells store data using alloy resistors in high-resistance amorphous and low-resistance crystalline states. The time of the memory cell'"'"'s set-current pulse can be 100 ns, much longer than read or reset times. The write time thus depends on the write data and is relatively long. A page-mode caching PCM device has a lookup table (LUT) that caches write data that is later written to an array of PCM banks. Host data is latched into a line FIFO and written into the LUT, reducing write delays to the relatively slow PCM. Host read data can be supplied by the LUT or fetched from the PCM banks. A multi-line page buffer between the PCM banks and LUT allows for larger block transfers using the LUT. Error-correction code (ECC) checking and generation is performed for data in the LUT, hiding ECC delays for data writes into the PCM banks.
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Citations
9 Claims
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1. A method for writing to a phase-change memory comprising:
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receiving from a host a burst write command including a host address and host data in a command buffer; comparing a portion of the host address to a plurality of tags in a lookup table and for storing the host data in the lookup table when a tag in the plurality of tags matches the portion of the host address; when the portion of the host address does not match any valid tag in the plurality of tags, allocating a new entry in the lookup table for the host address and storing the host data in the new entry; copying the host data from the lookup table to the phase-change memory by storing a data word data as binary bits each represented by a chalcogenide glass layer having a melting point that is higher than a crystallization point, the chalcogenide glass layer forming a variable resistor that alters a sensing current when a binary bit is read; and representing a first binary logic state using a crystalline state of the variable resistor and representing a second binary logic state using an amorphous state of the variable resistor for binary bits stored in the phase-change memory. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification