Random access memory employing read before write for...

Details Random access memory employing read before write for... Random access memory employing read before write for...

2009-02-16

2010-06-01

Dinh, Son (Department: 2824)

Static information storage and retrieval

Read/write circuit

Having particular data buffer or latch

C365S189011, C365S163000

Reexamination Certificate

active

07729179

ABSTRACT:
An improved architecture and method for operating a PCRAM integrated circuit is disclosed which seeks to minimize degradation in the resistance of the phase change material in the cells. When an attempt is made during a write command to write a data state to a bit which already has that data state, such matching data states are identified and writing to those bits is precluded during the write command. In one embodiment, both the incoming data to be written to a bit and the data currently present at that bit address are latched. These latched data are then compared (e.g., with an XOR gate) to determine which bits have a matching data state. The results of this comparison are used as an enable signal to the write (column) driver in the PCRAM memory array, with the effect that only data bits having different data state are written, while data bits having a matching data state are not needlessly re-written. Because matching data states are ignored, reliability problems associated with such redundant writing are alleviated, and power is saved.

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