SRAM with ROM functionality
First Claim
1. A circuit comprising:
- a plurality of memory cells configured to store both random access memory (RAM) data and read only memory (ROM) data; and
a select circuit coupled to the plurality of memory cells and configured to enable access to the RAM data or ROM data in response to an address signal.
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Accused Products
Abstract
A memory device including a first block of random access memory (RAM) cells having preprogrammed states, a second block of random access memory cells, and a select circuit configured to reset the first block of RAM cells to their preprogrammed states. When the first block of memory cells are reset to their preprogrammed states, the first block of memory cells may function as ROM memory cells that may be accessed at RAM speeds. The first block of RAM cells may not require additional nonvolatile circuitry in order to perform the ROM function; rather, the first block of RAM cells may each be configured to operate as both a volatile and nonvolatile memory cell using the same cell structure. For one embodiment, the select circuit alters the power applied to the first block of RAM cells to cause these RAM cells to perform a ROM function. Since, the first block of RAM cells may store RAM data when the device operates in RAM mode, and may store preprogrammed ROM data when reset by the select circuit, the first block of RAM cells may have a storage capacity that is greater than the number of RAM cells in the first block.
80 Citations
17 Claims
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1. A circuit comprising:
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a plurality of memory cells configured to store both random access memory (RAM) data and read only memory (ROM) data; and a select circuit coupled to the plurality of memory cells and configured to enable access to the RAM data or ROM data in response to an address signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16)
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15. A method of retrieving preprogrammed data from a random access memory (RAM) cell, comprising the step of:
cycling power applied to the RAM cell from a first voltage to a second voltage, and from the second voltage to the first voltage, wherein the second voltage is less than the first voltage, wherein the cycling step occurs in response to an address signal.
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17. A memory circuit comprising:
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a random access memory (RAM) address space implemented in a plurality of memory cells; a read only memory (ROM) address space implemented in the plurality of memory cells; and a select circuit configured to address the RAM address space or the ROM address space in response to an address signal.
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Specification