Mostek Corporation

Other

Xilinx, Inc.

Benchmarq Microelectronics, Inc.

Nec Corporation

Thomson Components-Mostek Corporation

Douglas P Sheppard

Harold L Davis

Scott S Nance

William Lau

Nicholas J Sawyer

A memory cell system/method incorporating reduced transistor counts and/or improved design-for-manufacturability (DFM) is disclosed. The system/method incorporates cross-coupled feedthru ()/feedback () amplifiers to implement memory cell state memory, wherein the feedback amplifier incorporates a multi-state output drive capability () allowing the memory cell to be read/written using only one access device () connected to the output () of the feedthru () amplifier. The multi-state output drive capability () modulates the feedback amplifier () drive strength to enable reading/writing of the feedthru amplifier () state with greatly reduced memory cell input fan-in requirements. The invention anticipates replacement of traditional DP/8T/6T/4T memory cell structures with corresponding 6T/6T/5T/3T memory cell configurations, resulting in a 16%-25% transistor reduction depending on memory array application context.

Memory cell system and method

A RAM with programmable data port configuration provides for programmable configuration of RAM data ports, and in the case of a multiport RAM, for independent programmable configuration of each data port. A single programmable RAM cell can be utilized in a variety of data port configurations, thereby reducing the number of combinations necessary in a standard cell library or gate array in implement the every possible configuration. In one embodiment of the invention, a dual port RAM is provided with a decoder, an input multiplexer and an output multiplexer for each data port. The input multiplexer for each data port provides several different selectable mappings of a RAM input word of varying sizes to the input bit lines of the respective data port. Similarly, the output multiplexer for each data port provides several different selectable mappings of the RAM output bit lines to the RAM output word. The decoder receives configuration programming bits to determine the appropriate size of the RAM input and output word for the respective port, and based on column addressing bits, outputs a select signal to select the appropriate mapping from the input and output multiplexers. Decoding circuitry is used during RAM write operations to disable those input bits not addressed.

Multiport RAM with programmable data port configuration

A memory array employing shared bit-lines. A memory is formed from an array of plural bit-cells organized as plural columns and plural rows. Plural word-lines are aligned with each for the rows, and each is electrically coupled to a discrete fraction of the bit-cells its corresponding row. The memory also includes plural bit-lines that are aligned with the plural columns. Every bit-line is electrically coupled to all of the bit-cells that lie along at least one column. In addition, at least a first one of the bit-lines is further electrically coupled to all of the bit-cells in an additional column. That bit-line is coupled such that every one of the plural bit-cells, that lie along any given row that are coupled to it, is coupled to a unique word-line from the other bit-cells coupled thereto. The shared bit-line invention is applicable to single and multiple port memory arrays. It is applicable to all memory array technologies including, but not limited to, SRAMs and DRAMs.

Shared bit line memory device and method

A memory device and method with reduced power consumption and improved noise performance. An illustrative embodiment provides a random access memory with an array of plural memory bit cells, having bit-latches coupled between bit-true pass-gates and bit-compliment pass-gates are organized as plural columns and rows. There are plural bit lines pairs aligned with the plural columns, each of the bit line pairs including a bit-true and a bit-compliment bit line. The bit cell pass-gates are electrically coupled to a bit-true and a bit-compliment line pair along each particular column. Plural word lines are aligned with the plural rows, each of the rows having an integer number, greater than one, of word lines aligned therewith. Each one of the integer numbers of word lines is electrically coupled to a fraction of the bit cells in its aligned row. The bit cell to word line coupling is arranged so that no two bit cells within each of the fractions of the plural bit cells are positioned adjacent to one another within the array.

Memory device and method with improved power and noise characteristics

A four-way cache data memory is provided, having a cache data RAM (30) and a tag RAM (28). The tag RAM (28) is enabled to access one of the tags therein. This tag is compared with the tag portion of the received memory address to determine if a tag is stored therein. If a true comparison results, a HIT is indicated and this is utilized to enable a portion of the cache data RAM (30). The data in the enabled portion is then output on the data bus.

Low power set associative cache memory

A RAM with programmable data port configuration provides for programmable configuration of RAM data ports, and in the case of a multiport RAM, for independent programmable configuration of each data port. A single programmable RAM cell can be utilized in a variety of data port configurations, thereby reducing the number of combinations necessary in a standard cell library or gate array to implement the every possible configuration. In one embodiment of the invention, a dual port RAM is provided with a decoder, an input multiplexer and an output multiplexer for each data port. The input multiplexer for each data port provides several different selectable mappings of a RAM input word of varying sizes to the input bit lines of the respective data port. Similarly, the output multiplexer for each data port provides several different selectable mappings of the RAM output bit lines to the RAM output word. The decoder receives configuration programming bits to determine the appropriate size of the RAM input and output word for the respective port, and based on column addressing bits, outputs a select signal to select the appropriate mapping from the input and output multiplexers. Decoding circuitry is used during RAM write operations to disable those input bits not addressed.

A four-way cache data memory is provided, having a cache data RAM (30) and a tag RAM (28). The tag RAM (28) is enabled to access one of the tags therein. This tag is compared with the tag portion of the received memory address to determine if a tag is stored therein. If a true comparison results, a HIT is indicated and this is utilized to enable a portion of the cache data RAM (30). The data in the enabled portion is then output on the data bus. Additionally, the data output of the cache data RAM (30) is inhibited unless it is determined that the cache data stored in the cache data RAM (30) is valid, this information stored in a status RAM (62).

Low power set associative cache memory with status inhibit of cache data

A circuit for presetting the voltage of an output terminal connected to an external load, where the output terminal receives either a high or a low voltage level state for output to the load during a data cycle, includes a voltage detector connected to the output terminal for sensing the voltage level at the output terminal at the end of the data cycle to determine whether the voltage level is at a high or a low voltage level state. A driver is connected to the voltage sensor for driving the voltage level at the output terminal prior to the start of a subsequent data cycle toward the opposite voltage state to a mid-level, as determined by the prior voltage state sensed by the voltage detector.

Circuit for presetting the voltage of an output terminal

A high speed parity circuit uses a sequence of simplified exclusive-OR circuits responsive to data input terminals containing a data signal and its complement and terminating in a sense amplifier, together with an operating sequence in which the inputs to the sequence are grounded while the data lines are first brought high and then set to the correct data state to form a pair of separate paths through the sequence when no current flows, after which set-up operation an input voltage circuit raises the voltage on one of the paths smoothly, so that the sense amplifier can respond as soon as its input is large enough, without waiting for a settling time.

High-speed parity check circuit

A read only memory circuit (10) includes an array of memory transistors including a row of such transistors (12-28) connected to a common word line (30). For each column of memory transistors there is provided a set of reference transistors which receive a word line signal which is concurrent with any word line signal provided to any word line in the memory array. Column decode signals (CD1-CD4) are provided to select a memory transistor on an activated word line and to select corresponding reference transistors. The memory transistor is fabricated to have one of a plurality of threshold voltages. The reference transistors are fabricated to have different predetermined threshold voltages. The drive signals are applied through the word lines concurrently to the selected memory transistor and corresponding reference transistors to cause the transistors to transition from a first state to a second state. Decoding circuitry is provided to determine the time sequence of transition of the memory transistor relative to the reference transistors. This decoding produces an output signal which corresponds to the threshold voltage and therefore the data state for the selected memory transistor.

Multi-bit read only memory circuit

A read only memory (ROM) circuit (10) includes a memory storage transistor (16) which is fabricated to have one of a plurality of threshold voltages corresponding to predetermined data states. The source and drain terminals of the memory transistor (16) are connected between a column node (18) and a bit line (20). A lightly depleted data transfer transistor (30) is connected between the bit line (20) and a data line (14). The column node (18), bit line (20) and data line (14) are precharged. A memory address is decoded to drive a selected word line (12) and a selected column decode line (32) to a high voltage state. A transistor (34) discharges the column node (18). Depending upon the state of the memory storage transistor (16) the bit line (20) is discharged or maintained precharged. The state of bit line (20) is transmitted through the data transfer transistor (30) to the data line (14). The data transfer transistor ( 30) can be fabricated as a relatively small device due to the large turn on voltage applied thereto because the transistor (30) is a depletion device. The smaller size of a plurality of the transistors (30) results in a substantial saving in space and reduces capacitive loading on the data line (14) thereby speeding up the discharge rate of the data line (14).

Semiconductor memory circuit with depletion data transfer transistor

A ROM circuit (10) includes a plurality of multi-bit memory storage transistors (22, 24, 26, 28, 29) and reference transistors (40, 42 and 44) all connected along a word line (16). Each of the storage transistors is provided with bit (18) and column (20) lines for activating a specific memory storage transistor and transmitting the data state thereof to sensing circuitry. A step control signal is transmitted through a control line (80) and applied to a selected one of the memory storage transistors and to each of the reference transistors (40, 42 and 44) on a selected word line (16). The step control signal is sequentially decreased in voltage to apply a progressively increasing gate-to-source voltage to each of the reference transistors (40, 42 and 44) and to a selected one of the memory storage transistors (26). The reference transistors (40, 42, and 44) are sequentially turned on by the increasing gate-to-source bias generated by the step control signal. The steps of the step control signal are generated in response to the turn on of the reference transistors (40, 42 and 44). The selected memory storage transistor (26) is turned on when the gate-to-source voltage of the transistor (26) is reached. At the time that the memory storage transistor (26) is turned on the condition of the reference transistors (40, 42 and 44) is latched to determine the voltage threshold level of the selected memory storage transistor (26). The latched conditions of the reference transistors (40, 42 and 44) are then decoded to produce the appropriate output signals corresponding to the data state fabricated into the selected memory storage transistor (26).

A semiconductor memory circuit (10) has a plurality of word lines (12, 14), column lines (16, 18) and bit lines (20, 22). A memory cell transistor (30) has the gate terminal connected to the word line (12) and the drain and source terminals connected between the bit line (20) and the column line (16). A reference transistor (106) is connected to the word line (12) to provide a reference signal for input to a sense amplifier (136). A data line (54) is connected to the bit line (20) to provide the data state from the data storage transistor (30) to the sense amplifier (136). The data bit line (20) and reference bit line (104) are clamped at different pull down voltages. The memory circuit (10) includes a reference circuit that has reference transistor (106) which operates statically to provide a reference signal for the sense amplifier (136). When the word lines are being sequentially accessed the reference signal produced by the reference circuit rises to a higher average voltage and enhances the operating speed of the memory.

Semiconductor memory circuit

A semiconductor memory address buffer (10) includes a plurality of serially connected inverter amplifier stages (76, 78, 80, and 82). An output stage (84) is connected to the last two inverter amplifier stages (80, 82). In the active mode of operation circuit (10) functions as a driver which receives an input address signal (A) and produces complementary output address signals (A, A). In a power down mode a group of transistors (18, 20 and 22) are turned off to deactive corresponding stages (76, 78 and 82) to terminate power consumption by these stages. A transistor (36) is activated to drive the input node (38) of a selected stage (80) to turn off a transistor (48) and essentially terminate power consumption by the selected stage (80). The output stage (84) receives differential inputs and functions in a push-pull configuration to produce the complementary output address signals (A, A). In the power down mode the buffer (10) has essentially zero power consumption while producing predetermined state complementary output signals (A, A).

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Southlake, TX, United States of America

Douglas P Sheppard