Converting SRAM cells to ROM cells
First Claim
1. A method of converting a static random access memory cell comprising a data retention portion powered by a higher and lower voltage supply line and comprising four transistors arranged as two cross coupled inverters to a read only memory cell said method comprising:
- severing a connection between at least one of said transistors within a first of said two inverters and one of said voltage supply lines such that when powered said first inverter outputs a predetermined value, andsevering a connection between a further transistor within a second of said two inverters and another of said voltage supply lines such that when powered said second inverter outputs a different predetermined value to said first inverter.
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Accused Products
Abstract
A method of converting a static random access memory cell to a read only memory cell and the cell thus converted is disclosed. The cell to be converted comprises a data retention portion powered by a higher and lower voltage supply line and four transistors arranged as two cross coupled inverters. It is converted to a read only memory cell by severing a connection between at least one of said transistors within a first of said two inverters and one of said voltage supply lines such that when powered said first inverter outputs a predetermined value.
12 Citations
16 Claims
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1. A method of converting a static random access memory cell comprising a data retention portion powered by a higher and lower voltage supply line and comprising four transistors arranged as two cross coupled inverters to a read only memory cell said method comprising:
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severing a connection between at least one of said transistors within a first of said two inverters and one of said voltage supply lines such that when powered said first inverter outputs a predetermined value, and severing a connection between a further transistor within a second of said two inverters and another of said voltage supply lines such that when powered said second inverter outputs a different predetermined value to said first inverter. - View Dependent Claims (2, 3)
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4. A method of converting a static random access memory cell comprising a data retention portion powered by a higher and lower voltage supply line and comprising four transistors arranged as two cross coupled inverters to a read only memory cell said method comprising:
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severing a connection between at least one of said transistors within a first of said two inverters and one of said voltage supply lines such that when powered said first inverter outputs a predetermined value, wherein said static random access memory cell further comprises two access transistors having different threshold voltages linking said data retention portion to respective bit lines, said static random access memory being a single ended sensing memory cell, and severing a connection between an output of said access transistor having a higher threshold voltage and one of said bit lines, said one of said bit lines being a bit line held at a predetermined voltage.
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5. A data storage cell comprising supply voltage lines connectable to a higher voltage source and a lower voltage source for powering said data storage cell, said data storage cell comprising:
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a data retention portion; said data retention portion comprising four transistors arranged as two cross coupled inverters, such that when powered a higher or lower voltage value is output from a first of said two inverters and the other lower or higher voltage value is output by a second of said two inverters, wherein said first inverter is arranged to be powered by only one of said two voltage sources, such that when said data storage cell is powered said first inverter outputs a predetermined one of said higher or lower voltage value dependent upon said voltage source powering said first inverter. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification