TSUJI YUKIHIDE (JP)
| WO2010106876A1 | 2010-09-23 |
| JP2006339395A | 2006-12-14 |
| CLAIMS What is claimed is: 1. A semiconductor device comprising: a reconfigurable circuit that includes three first wires coupled to a power line, a ground line, and either data line or data inverse line one-to-one; a second wire connected to one of inputs in a multiplexer; switch cells through which the said first wires are connected to said second wire, wherein every said switch cell is constructed of at least one non-volatile resistive switch that has two variable states of "ON" and "OFF". 2. The reconfigurable circuit according to claim 1 , wherein more than two said second wires are connected to said three first wires through said switch cells. 3. The reconfigurable circuit according to claims 1 or 2, further comprising another second wire that is connected to one of said inputs in said multiplexer, and said second wire that is connected only to said power and ground lines through said switch cells. 4. The reconfigurable circuit according to any one of claims 1-3, wherein every said switch cell is constructed of a non-volatile resistive switch and a first transistor: said first terminal of said non-volatile resistive switch is connected to said second wire; a second terminal of said non-volatile resistive switch is connected to a source terminal of said first transistor whose drain terminal is connected to said first wire; gate terminals of said first transistors in all switch cells on said second wire are connected to a first control signal line. 5. The reconfigurable circuit according to claim 4, wherein every said first wire is connected to a source terminal of a second transistor whose gate terminal is coupled to a second control signal line; all said drain terminals of second transistors are connected to a first program voltage line; every said second wire is connected to a source terminal of a third transistor whose gate terminal is coupled to said first control signal line; drain terminal of said third transistor is connected to a source terminal of a fourth transistor; all the gate terminals of said fourth transistors are connected to a write enable signal line; all the drain terminals of said fourth transistors are connected to a second program voltage line. The reconfigurable circuit according to any one of claims 1-3, wherein every said switch cell connected with the said first wire coupled to the said data line or data inverse line is constructed by a non-volatile resistive switch, wherein a first terminal of said non-volatile resistive switch is connected to said first wire while the second terminal is connected to said second wire; every said switch cell connected to said first wires coupled to the said power line and ground line is constructed of a non-volatile resistive switch and a first transistor, wherein a first terminal of said non-volatile resistive switch is connected to said second wire while a second terminal of said non-volatile resistive switch is connected to a source terminal of said first transistor whose drain terminal is connected to said first wire; the gate terminals of said first transistors in all switch cells on said second wire are connected to a first control signal line, 7. The reconfigurable circuit according to claim 6, wherein every said first wire coupled to the said data line or data inverse line is connected to a source terminal of a second transistor; all the gate terminals of the said second transistors are connected to a common second control signal line; every said first wire coupled to said power line and ground line is connected to a source terminal of a third transistor whose gate terminal is coupled to a third control signal line: all the drain terminals of the said second transistors and said third transistors are connected to a first program voltage line; every said second wire is connected to a source terminal of a fourth transistor whose gate terminal is coupled to the said first control signal, and a drain terminal of said fourth transistor is connected to a source terminal of a fifth transistor; all the gate terminals of said fifth transistors are connected to a write enable signal line; all the drain terminals of said fifth transistors are connected to a second program voltage line. 8. The reconfigurable circuit according to any one of claims 1-3, wherein every said switch cell is constructed two non-volatile resistive switches and a first transistor, wherein a first terminal of a first non-volatile resistive switch is connected to said second wire; a first terminal of a second non-volatile resistive switch is connected to the said first wire; a source of said first transistor is connected to a second terminal of said first non-volatile resistive switch as well as a second terminal of said second non-volatile resistive switch; the gate terminals of said first transistors in all switch cells on said second wires are connected to a first control signal line. 9. The reconfigurable circuit according to claim 8, wherein in said switch cells on a common said first wire, all the drain terminals of said first transistor are connected to a source terminal of a second transistor whose gate terminal is coupled to a second control signal line, and the common said first wire is connected to a source terminal of a third transistor whose gate terminal is coupled to said second control signal line, and all the drain terminals of said second transistors are connected to a first program voltage line, and all the drain terminals of said third transistors are connected to a second program voltage line; every said second wire is connected to a source terminal of a fourth transistor whose gate terminal is coupled to said first control signal, and all the drain terminals of said fourth transistors are connected to a third program voltage line. 10. The reconfigurable circuit according to any one of claims 1-3, wherein every said switch cell connected to said first wires coupled to said data line or data inverse line is constructed of two non-volatile resistive switches, wherein a first terminal of a first non-volatile resistive switch is connected to said first wire; a first terminal of a second non-volatile resistive switch is connected to said second wire; a second terminal of said first non-volatile resistive switch is connected to a second terminal of said second non-volatile resistive switch; every said nonvolatile switch cell connected to said first wires coupled to said power line and a ground line is constructed of two non-volatile resistive switches and a first transistor, wherein a first terminal of a first non-volatile resistive switch is connected to said first wire; a first terminal of a second non-volatile resistive switch is connected to said second wire; a source of said first transistor is connected to a second terminal of said first non-volatile resistive switch as well as a second terminal of said second non-volatile resistive switch; all the gate terminals of said first transistors in switch cells on one of said second wires are connected to a first control signal line. 11. The reconfigurable circuit according to claim 10, wherein in said switch cells on a common said first wire coupled to said data line or data inverse line, all said second terminals of said first non-volatile resistive switches are connected to a source terminal of a second transistor, and every said first wire coupled to said data input line or data inverse line is connected to a source terminal of a third transistor, and all the gate terminals of said second transistors and the third transistors are connected to a common second control signal; in said switch cells on a common said first wire coupled to said power line and a ground line, all the drain terminals of first transistors are connected to source terminal of a fourth transistor whose gate terminal is coupled to a third control signal line, and said common first wire coupled to said power line and a ground line are connected to a source terminal of a fifth transistor whose gate terminal is coupled to said third control signal line; all the drain terminals of said second and fourth transistors are connected to a first program voltage line, and all the drain terminals of said third and fifth transistors are connected to a second program voltage line; every said second wire is connected to a source terminal of a sixth transistor whose gate terminal is coupled to said first control signal line, and all the drain terminals of the said sixth transistors are connected to a third program voltage. 12. The reconfigurable circuit according to any one of claims 1-11 , wherein ON/OFF resistance ratio of said non-volatile resistive switch is over 104. 13. The reconfigurable circuit according to any one of claims 1-11 , wherein every said non-volatile resistive switch comprices a metal oxide resistance change device or a solid electrolyte resistance change device. 14. A method to utilize the reconfigurable circuit according to any one of claims 1-11 for a specific application; the method comprising: configuring said switch cells connected to said first wires coupled to said power line and the said ground line as "ON" or "OFF" states randomly; and configuring all said switch cells connected to said first wire coupled to said data line or data inverse line as a same state. |
RECONFIGURABLE CIRCUIT
Technical Field
[0001]
This invention is about a reconfigurable circuit using non-volatile resistive switches.
Background Art
[0002]
Field-programmable gate arrays (FPGAs) are widely used for low- and medium-volume chips, but they have failed dominate over the high-volume market, because of their high cost which results from a large silicon area of the device. The most common FPGA architecture consists of an array of logic blocks (LBs), I/O pads, and routing channels. In the LB, look-up table (LUT) is used as a "soft" function generator to realize various functions, which leads to very high functionality but causes large area of the device. It has been shown that a simple look-up table (LUT)/flip-flop (FF) FPGA requires about 35 times the area of a cell-based application-specific integrated circuit (ASIC). To narrow this gap, frequently used dedicated "hard" circuits such as carry chains, adders and multipliers have been employed in FPGA design as shown in the non-patent document 1.
[0003]
The "soft" LUT is conventionally constructed by a multiplexer (MUX), while a "hard" circuit can also be constructed by a MUX if pass transistor logic (PTL) is used. The "hard" circuits are very efficient when they are used.
Otherwise, they are wasted. To overcome the negative impact of the "hard" circuit, concept of sharing common MUX to implement "soft" and "hard" circuits has been introduced in the non-patent document 2. [0004]
As shown in FIG.1A, a 2 n :1 MUX 101 is shared to construct a
reconfigurable circuit to implement a LUT and a "hard" circuit. A MUX input switch block 102 selects either a memory value or a data input (or its inverse) as the input of the MUX 101 for a LUT mode or a "hard" circuit mode. The MUX input switch block 102 is composed of a memory m s and nMOS pass transistors Tr in conventional CMOS technology as shown in patent document 1. The nMOS transistors Tr are connected to the two-state memories mi ni 2 n as shown in FIG. 1 B. When the m s is configured as "1", memories m-i,..., ιτΐ 2 Π are connected with the 2 n :1 MUX 10rs input ports Vi, V 2 n , so that n-input LUT can be implemented. When the m s is configured as "0", data input D and its inverse ~D are applied to the 2 n :1 MUX 101 ' s input ports V-i, V2 n , so that a "hard circuit" can be implemented. The 2 n :1 MUX 101 can be efficiently utilized. However, the MUX input switch block 102 causes large area of the device.
[0005]
As a basic "hard" circuit, a full adder (FA) is used to construct multi-bit adder and multiplier in conventional FPGAs. As shown in FIG.2A, an 8:1 MUX 201 is shared to implement a 3-input LUT and the FA, which leads to high .
utilization of the hardware resources. The 8:1 MUX 201 has one output and two intermediate outputs, wherein signals A and B select one input from among inputs Vi, V 4 as the intermediate OUT| M i, signals A and B select one input from among inputs V 5 , V 8 as the intermediate OUT| M2 , signal M select one of OUTI I and OUTIM2 as a final output OUT. When the m s is configured as "1", memories mi,..., m 8 are connected with the 8:1 MUX 201 ' s input ports \ , V 8) so that 3-input LUT can be implemented. When the m s is configured as "0", carry input Cm and its inverse ~C in are applied to the 8:1 MUX201's input ports \ , V 8 , so that the FA can be implemented according to the truth table shown in FIG. 2B. The MUX input switch block 202 is composed of 12 nMOS transistors Tr and a memory M s constructed by 6 transistors (if a conventional SRAM is used), which results in large area of the device.
[0006]
Non-patent document 1 : P. A. Jamieson and J. Rose, "Enhancing the area efficiency of FPGAs with hard circuits using shadow clusters," IEEE
Transactions on Very Large Scale Integration (VLSI) Systems, vol. 18, no. 12, pp. 1696-1709, Dec. 2010.
Non-patent document 2: X. BAI, M. KAMEYAMA, Implementation of
Voltage-Mode/ Current-Mode Hybrid Circuits for a Low-Power Fine-Grain
Reconfigurable VLSI , IEICE TRANSACTIONS on Electronics, Vol.E97-C, No.10, pp.1028-1035
Non-patent document 3: Shunichi Kaeriyama et al., A Nonvolatile Programmable Solid-Electrolyte Nanometer Switch, IEEE Journal of Solid-State Circuits, Jan. 2005, pp. 168-176, vol. 40, No. 1.
Patent document : US 7019557
Patent document 2: US 8816312
Summary of the Invention
Problem to be Solved by the Invention
[0007]
The object of the present invention is to provide a compact
reconfigurable circuit implementing a LUT and a "hard" circuit.
The present invention provides a reconfigurable circuit comprising: first wires disposed in a first direction; a second wire disposed in a second direction intersecting the first direction; a power line, a ground line and data input line or data input inverse line coupled to the said first wires one-to-one; a multiplexer, one of whose inputs is connected with the second wire; nonvolatile switch cells utilized to interconnect the first wires and second wire at the crosspoints, wherein every nonvolatile switch cell is constructed by at least one non-volatile resistive switch.
According to the reconfigurable circuit by the present invention, a device having a small area can be realized.
Means for Solving the Problem
[0008]
Brief Description of the Drawings
[0009]
The invention will now be described with reference to the accompanying drawings.
FIG.1A illustrates a conventional reconfigurable circuit implementing a LUT and "hard" circuit.
FIG. 1 B shows an output state of memory M n in FIG. 1A.
FIG.2A illustrates a conventional FA-type 3-input LUT implementing a 3-input LUT and the FA.
FIG. 2B shows a truth table of FA in FIG. 2A.
FIG.3A illustrates a novel nonvolatile-switch-cell (NVSC)-based reconfigurable circuit according to embodiment 1.
FIG. 3B shows an output state of memory M n in FIG. 3A.
FIG.4 A illustrates a NVSC using 1 transistor 1 non-volatile resistive switch (1T1 R) structure.
FIG.4 B illustrates a NVSC using 1 transistor 2 non-volatile resistive switches (1T2R) structure.
FIG.4 C illustrates a 1T1 R-NVSC array.
FIG.4 D illustrates a 1T2R-NVSC array.
FIG.5 illustrates a novel 1T1 R-NVSC-based reconfigurable circuit implementing a LUT and "hard" circuit according to embodiment 1.
FIG.6 illustrates a novel 1T1 R-NVSC-based FA-type 3-input LUT implementing a 3-input LUT and the FA according to embodiment 2. FIG.7 illustrates a novel select-transistor-shared 1T R-NVSC-based FA-type 3-input LUT implementing a 3-input LUT and the FA according to embodiment 3.
FIG.8 illustrates a novel 1T2R-NVSC-based FA-type 3-input LUT implementing a 3-input LUT and the FA according to embodiment 4.
FIG.9 illustrates a novel select-transistor-shared 1T2R-NVSC-based FA-type 3-input LUT implementing a 3-input LUT and the FA according to embodiment 4.
FIG.10 illustrates transistor count comparison of FA-type 3-input LUTs. FIG.11 illustrates a novel logic block (LB) using the novel NVSC-based
FA-type 3-input LUTs according to embodiment 5.
Best Mode for Carrying Out the Invention
[0010]
Embodiment 1
A first exemplary embodiment of the present invention will be described.
FIG.3A illustrates a novel non-volatile-switch-cell (NVSC)-based reconfigurable circuit composed of wires, NVSCs and a MUX 301. First wires are disposed in a first direction, while a second wire is disposed in a second direction intersecting the first direction. Vdd, Gnd, data input D or input inverse ~D are applied to the first wires one-to-one, while the second wire is coupled to one input port V n of the MUX 301. NVSCs interconnect the first and second wires at the crosspoints. At one crosspoint, one terminal of a NVSC is connected to one of the first wires, while the other one is connected to said second wire.
[0011]
FIG. 3B shows an output state of memory M n , a tri-state memory M n is constructed of two NVSCs: one is connected to Vdd and the other one is connected to Gnd. When the NVSC connected to Vdd, it is configured as "ON" and the NVSC that is connected to Gnd is configured as "OFF", M n provides the Vdd state. When the NVSC connected to Vdd is configured as "OFF" and the NVSC that is connected to Gnd is configured as "ON", M n provides the Gnd state. When both the NVSCs are configured as "OFF", M n provides a high impedance state as well. Therefore, the nMOS pass transisors that provide a high
impedance state for memories in a conventional reconfigurable circuit can be omitted.
[0012]
The NVSC is constructed of at least one or more non-volatile resistive switches (NVRSs). The NVRS has ON and OFF states, and the ON/OFF resistance ratio is over 10 4 . There are mainly two kinds of NVRSs, one is
ReRAM (Resistance Random Access Memory) using the transition metal oxide, the other one is Nano Bridge (registered trademark of NEC Corporation) using the ion conductor. The NVRS is stacked on a CMOS logic circuit, which result in a devicehaving a very small area. As well, non-volatility reduces the stand-by power. Also, its small resistance and capacitance contribute to high speed.
FIG.4 illustrates two kinds of NVSC arrays: a 1-transistor 1 NVRS (1T1 R) array (FIG.4A) and a 1-transistor 2 NVRSs (1T2R) NVRC array (FIG.4B).
[0013]
In the 1T1 R-NVSC array shown in FIG.4C, every 1T1 R-NVSC has 2 terminals, where a first terminal is connected to a first wire disposed in a first direction, while a second terminal is connected to a second wire disposed in a second direction intersecting the first direction. One terminal of the NVRS in the 1T1 R-NVSC is connected to the source of a transistor whose gate is connected to a control signal Ctrl x , and the drain is connected to the first wire. The transistor works as a switch to access the selected 1T1 R-NVSC and to isolate unseiected 1T1R-NVSCs for high write reliability as shown in the non-patent document 3. Only when the transistor is switched ON, can the selected 1T1 R-NVSC be configured. [0014]
The configuration and operation modes of the 1T1 R-NVSC array will be discussed as follows. The programming voltages PV X and PV y are used to configure NVSCs as "ON" or "OFF". The control signals Ctrl x and Ctrl y determine the address of the NVSC to be configured. The write enable signal WE is used to enable the configuration mode. In the configuration mode, for example, in order to program NVSC (1 , 1) as "ON", PV X and PV y are set to Vset (Set voltage for NVRS) and Gnd, respectively. WE, Ctrl x1 and Ctrl y1 are set to "1", and Ctrl x0 and Ctrlyo are set to "0". Vset and Gnd are applied to the two terminals of the NVSC (1 , 1) which can be configured as "ON". On the other hand, if we want to program NVSC (1 , 1) as "OFF", PV X and PV y are set to Gnd and Vreset (reset voltage for NVRS), respectively. In the operation mode, WE, Ctrl y0 and Ctrl y i are set to "0" to turn off PV X and PV y , and Ctrl x0 and Ctrl x1 are set to "1" to turn on a data transfer path, so that data inputs can be switched according to "ON OFF" of 1T1 R-NVSCs.
[0015]
To improve OFF-state reliability of the 1T1 R-NVSC, 1T2R-NVSC has been introduced in US8816312. As shown in FIG.4B, two NVRSs are connected in series in the opposite direction, in which the two OFF-state NVRSs
complementarily divide the voltage stress, greatly enlarging the OFF-state lifetime. NVRS count is increased twice in comparison with the 1T1 R-NVSC, but the area of the device is not increased because the additional NVRS is stacked on the CMOS circuit. In the 1T2R-NVSC array shown in FIG.4D, the common terminal of the two serially-connected NVRSs is connected to the source of a transistor whose gate is connected to a control signal Ctrl x , and the drain is connected with the control signal Ctrl y . The transistor works as a switch to access the selected 1T2R-NVSC and to isolate unselected 1T2R-NVSCs for high write reliability. Only when the transistor is switched ON, can the selected 1T2R-NVSC be configured. The disadvantage of the 1T2R-NVSC is that three programming voltages need to be configured, while only two programming voltages are necessary to configurethe 1T1R-NVSC.
[0016]
Next, the configuration and operation modes of the 1T2R-NVSC array will be discussed. The programming voltages PV X , PV y and PV Z are used to configure NVSCs as "ON" or "OFF". The control signals Ctrl x and Ctrl y determine the address of the NVSC to be configured. In the configuration mode, for example, in order to program NVSC (1 , 1) as "ON", PV X , PV y and PV Z are set to Vset, Vset and Gnd, respectively. Ctrl x i and Ctrl y1 are set to "1", and Ctrl x0 and Ctrl y o are set to "0". Vset and Gnd are applied to the three terminals of the NVSC (1 , 1) which can be configured as "ON". On the other hand, in ordre to program NVSC (1 , 1) as "OFF", PV X , PV y and PV Z are set to Gnd, Gnd and Vreset, respectively. In the operation mode, all the Ctrl x o, Ctrl x i , Ctrl y o and Ctrl y i are set to "0", so that data inputs can be switched according to "ONTOFF" of
1T2R-NVSCs.
[0017]
Embodiment 2
Next, a second embodiment according to the present invention will be presented. The present embodiment discloses a novel reconfigurable circuit using 1T1R-NVSCs.
[0018]
FIG.5 illustrates a novel 1T R-NVSC-based reconfigurable circuit implementing a LUT and "hard" circuit according to the exemplary embodiment. The novel 1T1 R-NVSC-based reconfigurable circuit is composed of wires,
1T1R-NVSCs and a 2 n :1 MUX 501 , 1T1R-NVSCs constructs MUX input switch block 502, and memories M 1 ,...,M 2 n . First wires are disposed in a first direction, while second wires are disposed in a second direction intersecting the first direction. Vdd, Gnd, data signal D, and data signal inverse ~D are applied to the first wires one-to-one, while the second wires are coupled to the input ports Vi, V 2 , V 2 n of the MUX 501 one-to-one. A first group of the first wires are coupled to Vdd and Gnd, and a second group of the first wires are coupled to D and ~D.
[0019]
At the crosspoints of the first group of the first wires and the second wires, 1T1 R-NVSCs are fully arranged to construct memories Mi, . . . ,M2 n to provide Vdd, Gnd and high impedance states randomly whereas at the crosspoints of the second group of the first wires and the second wires,
T1 R-NVSCs are sparsely arranged to apply D/~D to the MUX 501 input ports according to dedicated "hard" circuit.
[0020]
When Vdd or Gnd is selected as the input of the MUX 501 , memories Mi, M 2 n are applied to the MUX 501 , thus LUT can be realized. On the other hand, when D/~D is selected as the input of the MUX 501 , a PTL "hard" circuit can be realized.
[0021]
In comparison with the conventional reconfigurable circuit shown in FIG.1 , the area of the MUX input switch block can be reduced, because all the NVRSs are stacked on the CMOS circuit and the transistor count is reduced by more than half in the present embodiment.
[0022]
FIG.6 illustrates a novel 1T1 R-NVSC-based FA-type 3-input LUT to implement a 3-input LUT and the FA. The n defined in the first embodiment is set as 3 in the present embodiment. The "hard" circuit is set as the FA.
1T1 R-NVSCs are arranged at the crosspoints (C in , V^, (~C in , V 2 ), (~C in , V 3 ), (C in , V 4 ), (Cin, V 6 ) and (C in , V 7 ) for implementation of the FA. In ordert to implement the FA, all the 1T1 R-NVSCs in the MUX input switch block 602 are configured as "ON", the memory M5 is configured as the Vdd state, the memory M8 is configured as Gnd state, and the other memories are configured as the high impedance state. The C in and ~C in are applied to the 8:1 MUX 60 , and SUM and Cout will be generated, simultaneously. On the other hand, in order to implement a 3-input LUT, all the 1T1 R-NVSCs in the MUX input switch block are configured as the OFF state, and the memories Mi Ms are configured as the
Vdd or Gnd state randomly depending on the 3-variable function that is required.
[0023]
In comparison with the conventional FA-type 3-input LUT shown in FIG.2, the area of the MUX input switch block 602 can be reduced in the novel 1T1 R-NVSC-based FA-type 3-input LUT according to the present embodiment, because the NVRSs are stacked on CMOS circuit and the transistor count of the MUX input switch block is reduced by 66.7% (in case that m s in FIG.2 is a SRAM composed of 6 transistors). Total transistor count is reduced by 29.5%.
[0024]
Embodiment 3
Next, a third embodiment according to the present invention will be presented. The present embodiment discloses a novel select-transistor-shared 1T1 R-NVSC-based FA-type 3-input LUT. Transistor count in the MUX input switch block can be further reduced.
[0025]
Sharing the control signals Ctrl y o and Ctrl y i and sharing selected transistors in the MUX input switch block in order to further reduce the transistor count without reducing write reliability constitutes the difference between the second and third embodiment.
[0026]
FIG.7 illustrates the novel select-transistor-shared 1T1 R-NVSC-based FA-type 3-input LUT implementing a 3-input LUT and the FA. As mentioned in embodiment 2, the 1T1 R-NVSCs in the memories are configured as "ON" or "OFF" randomly according to the function that is required. Write disturbance problems may occur when there is no isolation between NVRSs. However, all the 1T1 R-NVSCs in the MUX input switch block 702 are configured to be in the same "ON" or "OFF" state, so that it is not necessary to isolate the NVRSs. Therefore, the control signal Ctrl y o and select transistors T1 and T2 are shared by the 6 NVRSs in the MUX input switch block 702 that is to be configured. There are two advantages, one is area reduction, and the other one is write cycle count reduction.
[0027]
Total transistor count of the select-transistor-shared 1T1 R-NVSC-based FA-type 3-input LUT is reduced by 9.7% in comparison with that of the
1T R-NVSC-based FA-type 3-input LUT shown in FIG.6 according to the second embodiment.
[0028]
Embodiment 4
Next, a forth embodiment according to the present invention will be presented. The present embodiment discloses a the reconf ' igurable circuit using 1T2R-NVSCs.
[0029]
FIG.8 illustrates a novel 1T2R-NVSC-based FA-type 3-input LUT to implement a 3-input LUT and the FA. 1T2R-NVSCs are arranged at the crosspoints (Cm, i), (~C in , V 2 ), (~C in , V 3 ), (C in , V 4 ), (C in , V 6 ) and (C in , V 7 ) to implement the FA. In order to implement the FA, all the 1T2R-NVSCs in the MUX input switch block are configured as "ON", memory M5 is configured as a Vdd state, memory M8 is configured as a Gnd state, and the other memories are configured as a high impedance state. The C in and ~C in are applied to the 8:1 MUX 801 , and SUM and C ou t will be generated, simultaneously. On the other hand, in order to implement a 3-input LUT, all the 1T2R-NVSCs in the MUX input switch block 802 are configured as the OFF state, and the memories Mi M 8 are configured as the Vdd or the Gnd state randomly depending on the
3-variable function we need.
[0030]
In comparison with the conventional FA-type 3-input LUT shown in FIG.2, the area of the MUX input switch block 802 can be reduced in the novel 1T2R-NVSC-based FA-type 3-input LUT according to the present embodiment, because the NVRSs are stacked on a CMOS circuit and the transistor count of the MUX input switch block 802 is reduced by 66.7% (in case that m s in FIG.2 is a SRAM composed of 6 transistors). Total transistor count is reduced by 34.1%.
[0031]
FIG.9 illustrates a novel select-transistor-shared 1T2R-NVSC-based FA-type 3-input LUT implementing a 3-input LUT and the FA. The 1T2R-NVSCs in the memories are configured as "ON" or "OFF" randomly according to the function that is required. Write disturbance problem may occur when there is no isolation between these NVRSs. However, all the 1T2R-NVSCs in the MUX input switch block 902 are configured to be in the same "ON" or "OFF" state, so that isolation between the NVRSs are not needed. Therefore, the control signal Ctrlyo and select transistors T1 , T2, T3 and T4 are shared by the 6 NVRSs in the MUX input switch block 902 that is to be configured. There are two advantages, one is area reduction, and the other one is write cycle count reduction. In the T2R-NVSC-based FA-type 3-input LUT shown in FIG.8 according to the second embodiment, 6 cycles are necessary to configure the 6 NVRSs in the MUX input switch block 902, whereas in the select-transistor-shared
1T2R-NVSC-based FA-type 3-input LUT, only one cycle is necessary to configure all the 6 NVRSs.
[0032] Total transistor count of the select-transistor-shared 1T2R-NVSC-based FA-type 3-input LUT is reduced by 10.3% in comparison with that of the
1T2R-NVSC-based FA-type 3-input LUT shown in FIG.8. Total transistor count of the select-transistor-shared 1T2R-NVSC-based FA-type 3-input LUT is reduced by 7.1 % in comparison with that of the select-transistor-shared
1T1 R-NVSC-based FA-type 3-input LUT shown in FIG.7.
[0033]
Embodiment 5
Next, a fifth embodiment according to the present invention will be presented. The present embodiment discloses a novel LB using novel
NVSC-based FA-type 3-input LUTs. The novel NVSC-based FA-type 3-input LUT can be the novel 1T1 R-NVSC-based FA-type 3-input LUT according to embodiment 2, the novel select-transistor-shared T R-NVSC-based FA-type 3-input LUT according to embodiment 3, the novel 1T2R-NVSC-based FA-type 3-input LUT according to embodiment 4, or the novel select-transistor-shared 1T2R-NVSC-based FA-type 3-input LUT according to embodiment 4.
[0034]
FIG.11 illustrates the novel LB using the novel NVSC-based FA-type 3-input LUTs to implement a 4-bit adder and 4 3-input LUTs. The novel LB is composed of 4 basic logic elements (BLEs). The BLE is composed of one novel NVSC-based FA-type 3-input LUT, two D-flip-flops (DFFs) and two MUXs. The novel NVSC-based FA-type 3-input LUT is used to implement a 1-bit adder and a 3-input LUT. The DFF is used to store the result of the novel NVSC-based FA-type 3-input LUT. The MUX is used to select the result stored in the DFF or the result of the novel NVSC-based FA-type 3-input LUT as output of the BLE.
[0035]
In a logic mode, BLE1 , BLE2, BLE3 and BLE4 are used to realize various functions of data inputs (A 0 , B 0 , M 0 ), (Ai, B 1 f Mi), (A 2 , B 2 , M 2 ), and (A 3 , B 3 , M 3 ), respectively. To implement a 4-bit adder of data inputs A and B, (A 0 , B 0 ), (A-i, Bi), (A 2 , B 2 ), and (A 3 , B 3 ) are applied to the first novel NVSC-based FA-type 3-input LUT in BLE1 , the second novel NVSC-based FA-type 3-input LUT in BLE2, the third novel NVSC-based FA-type 3-input LUT in BLE3, and the forth novel NVSC-based FA-type 3-input LUT in BLE4, respectively. A carry-in signal C in is applied to the first novel NVSC-based FA-type 3-input LUT in BLE1 whose carry-out signal Ci is directly applied to the second novel NVSC-based FA-type 3-input LUT in BLE2. Then the carry-out signal C 2 of the second novel
NVSC-based FA-type 3-input LUT in BLE2 is directly applied to the third novel NVSC-based FA-type 3-input LUT in BLE3 whose carry-out signal C 3 is directly applied to the forth novel NVSC-based FA-type 3-input LUT in BLE4. Finally, the forth novel NVSC-based FA-type 3-input LUT in BLE4 generates the carry-out signal C 0 UT- [0036]
This embodiment does not limit adding to four-bit numbers because the
LB is formed as part of an array of LBs, and higher-order bits may be handled in LBs connected above the shown CLB.
[0037]
It is apparent that the present invention is not limited to the above embodiments, but may be modified and changed without departing from the scope and spirit of the invention.