TWI860632B - Memory device and in-memory search method thereof - Google Patents

Abstract

A memory device and an in-memory search method are provided. The memory device includes a first memory cell block, a second memory cell block, at least one search memory cell pair and a sense amplifier. The search memory cell pair includes a first search memory cell and a second search memory cell, wherein the first search memory cell and the second search memory cell are respectively disposed in the first memory cell block and the second memory cell block. The first search memory cell and the second search memory cell respectively receive a first search voltage and a second search voltage, where the first search voltage and the second search voltage are generated according to a searched data. The sense amplifier generates a search result according to currents on a first bit line and a second bit line.

Description

Memory device and memory search method thereof

The present invention relates to a memory device and a method for searching in the memory, and in particular to a memory device and a method for searching in the memory capable of increasing the length of search data.

With the rise of hardware accelerators for big data and artificial intelligence, data matching/searching has become an indispensable function. In the existing technology, the so-called ternary content addressable memory (TCAM) can achieve highly parallel data search. The ternary content addressable memory in the known technology is often composed of static memory, so it often has problems of insufficient storage density and high power consumption.

In response to this, the learning technology proposes to use non-volatile memory to implement ternary content addressable memory. However, in the learning technology, two non-volatile memory cells are always required to store a piece of storage data. When performing a search action, the two non-volatile memory cells need to occupy two word lines, resulting in the data length of the data to be searched being reduced during the search action.

The present invention provides a memory device and a memory search method thereof, which can increase the data length of the data to be searched and improve the efficiency of the search action.

The memory device of the present invention is used to perform an internal search operation. The memory device includes a first memory cell block, a second memory cell block, at least one search memory cell pair and a sense amplifier. The search memory cell pair includes a first search memory cell and a second search memory cell, wherein the first search memory cell and the second search memory cell are respectively arranged in the first memory cell block and the second memory cell block, and the first search memory cell and the second search memory cell respectively receive a first search voltage and a second search voltage, wherein the first search voltage and the second search voltage are generated according to the desired search data. The sense amplifier is coupled to the first search memory cell and the second search memory cell respectively through the first bit line and the second bit line, and generates a search result according to the signals on the first bit line and the second bit line.

The in-memory search method of the present invention includes: respectively setting a first search memory cell and a second search memory cell in a first memory cell block and a second memory cell block; making the first search memory cell and the second search memory cell form a search memory cell pair, wherein the first search memory cell and the second search memory cell respectively receive a first search voltage and a second search voltage data, and the second search voltage is generated according to the desired search data; and providing a sensing amplifier to generate a search result according to the signals provided by the first search memory cell and the second search memory cell respectively through a first bit line and a second bit line.

Based on the above, the memory device of the present invention arranges the first search memory cell and the second search memory cell in the search memory cell pair in different memory cell blocks. In this way, the number of bits of the search data that can be received by the word line of the memory cell block can be doubled, which effectively increases the data length of the search data in the memory and improves the efficiency of the search action.

Please refer to FIG. 1 , which shows a schematic diagram of a memory device of an embodiment of the present invention. The memory device 100 is used to perform an internal search operation. The memory device 100 has memory cell blocks 110 and 120. The memory cell block 110 includes a plurality of search memory cells CA1 to CA8, and the memory cell block 120 includes a plurality of search memory cells CB1 to CB8. Among them, the search memory cells CA1 to CA4 are coupled to the same bit line BLA1, and the search memory cells CA5 to CA8 are coupled to the same bit line BLA2. Search memory cells CA1 and CA5 are coupled to the same word line WLA1; search memory cells CA2 and CA6 are coupled to the same word line WLA2; search memory cells CA3 and CA7 are coupled to the same word line WLA3; search memory cells CA4 and CA8 are coupled to the same word line WLA4. Search memory cells CA1, CA2, CA5, and CA6 share the same source line SLA1, and search memory cells CA3, CA4, CA7, and CA8 share the same source line SLA2.

In addition, search memory cells CB1-CB4 are coupled to the same bit line BLB1, and search memory cells CB5-CB8 are coupled to the same bit line BLB2. Search memory cells CB1 and CB5 are coupled to the same word line WLB1; search memory cells CB2 and CB6 are coupled to the same word line WLB2; search memory cells CB3 and CB7 are coupled to the same word line WLB3; search memory cells CB4 and CB8 are coupled to the same word line WLB4. Search memory cells CB1, CB2, CB5, and CB6 share the same source line SLB1, and search memory cells CB3, CB4, CB7, and CB8 share the same source line SLB2.

In this embodiment, the memory device 100 may be a NOR flash memory.

In the present embodiment, two search memory cells disposed in different memory cell blocks 110 and 120 can form a search memory cell pair. For example, search memory cells CA1 and CB1 can form a search memory cell pair; search memory cells CA2 and CB2 can form a search memory cell pair; ...; search memory cells CA8 and CB8 can form a search memory cell pair. Taking the paired search memory cells CA1 and CB1 as an example, the search memory cells CA1 and CB1 can receive a first search voltage and a second search voltage through word lines WLA1 and WLB1, respectively. The first search voltage and the second search voltage can be generated according to the desired search data. The search memory cells CA1 and CB1 can respectively determine whether to generate current according to the received first search voltage and second search voltage.

The memory device 100 further includes sense amplifiers SA1 and SA2. The sense amplifier SA1 is coupled to the bit lines BLA1 and BLB1, and senses the currents on the bit lines BLA1 and BLB1 to generate a search result R1. The sense amplifier SA2 is coupled to the bit lines BLA2 and BLB2, and senses the currents on the bit lines BLA2 and BLB2 to generate a search result R2.

Please refer to FIG. 2A, which is a schematic diagram of an implementation of a memory search action of an embodiment of the present invention. In FIG. 2A, a memory device 200 includes memory cell blocks 210 and 220. The memory cell block 210 has bit lines BLA1 to BLA3, and a plurality of search memory cells are coupled to each of the bit lines BLA1 to BLA3. The memory cell block 220 has bit lines BLB1 to BLB3, and a plurality of search memory cells are coupled to each of the bit lines BLB1 to BLB3. The multiple search memory cells in the memory cell block 210 are paired with the multiple search memory cells in the memory cell block 220 to form a search memory cell pair. The pairing method has been described in detail in the embodiment of FIG. 1 and will not be described in detail here.

In this embodiment, the memory device 200 further includes sense amplifiers SA1-SA3. The sense amplifier SA1 is coupled to the bit lines BLA1 and BLB1; the sense amplifier SA2 is coupled to the bit lines BLA2 and BLB2; and the sense amplifier SA3 is coupled to the bit lines BLA3 and BLB3.

In this embodiment, each search memory cell pair in the memory device 200 can record single-bit data. In the memory cell block 210, when the storage data of the search memory cell is a logical value 1, the search memory cell can be set to have a first critical voltage; conversely, when the storage data of the search memory cell is a logical value 0, the search memory cell can be set to have a second critical voltage, wherein the first critical voltage is greater than the second critical voltage. In the memory cell block 220, when the storage data of the search memory cell is a logic value 1, the search memory cell can be set to have a second critical voltage; conversely, when the storage data of the search memory cell is a logic value 0, the search memory cell can be set to have a first critical voltage. It is worth mentioning that when the stored data of the search memory cell is don't care (or wild card), the search memory cells in the search memory pair have a relatively high first critical voltage. When the stored data of the search memory cell is invalid, the search memory cells in the search memory pair have a relatively low second critical voltage. The state of the stored data and the critical voltage of the search memory cell in the search memory pair can be seen in the truth table shown below: Save data Search memory cells in memory cell block 210 Search memory cell block 220 for memory cells 0 LVT HVT 1 HVT LVT Don't care about "X" HVT HVT Invalid "-" LVT LVT Among them, HVT is the relatively high first critical voltage, and LVT is the relatively low second critical voltage.

In the present embodiment, the search memory cells on the bit lines BLA1 and BLB1 may store the logical values 1, 0, 1, 1, 0, 1, 0, 1, respectively, from the top to the bottom of the figure. Therefore, the critical voltages of the search memory cells on the bit line BLA1 may be HVT, LVT, HVT, HVT, LVT, HVT, LVT, HVT, respectively, from the top to the bottom of the figure. The critical voltages of the search memory cells on the bit line BLB1 may complement the critical voltages of the search memory cells on the bit line BLA1, and may be LVT, HVT, LVT, LVT, HVT, LVT, HVT, LVT, HVT, LVT, respectively.

In addition, the search memory cells on the bit lines BLA2 and BLB2 may store the logical values 1, 0, 0, 0, 0, 1, 0, 1, respectively, from the top to the bottom of the diagram. Therefore, the critical voltage of the search memory cell on the bit line BLA2 may be HVT, LVT, LVT, LVT, LVT, HVT, LVT, HVT, HVT, respectively, from the top to the bottom of the diagram. The critical voltage of the search memory cell on the bit line BLB2 may complement the critical voltage of the search memory cell on the bit line BLA2, and may be LVT, HVT, HVT, HVT, HVT, HVT, LVT, HVT, LVT, LVT, respectively. The search memory cells on the bit lines BLA3 and BLB3 may store the logical values X, -, 0, 1, 0, 1, 0, 1, respectively, from the top to the bottom of the diagram. Therefore, the critical voltages of the search memory cells on the bit line BLA3 may be HVT, LVT, LVT, HVT, LVT, HVT, LVT, HVT, respectively, from the top to the bottom of the diagram. The critical voltages of the search memory cells on the bit line BLB3 may complement the critical voltages of the search memory cells on the bit line BLA3, and may be HVT, LVT, HVT, LVT, HVT, LVT, HVT, LVT, respectively.

When performing a search operation in the memory, taking the search data SD as 1, 0, 0, 0, 0, 1, -, X as an example, the memory device 200 can generate corresponding search voltages SS1 and SS2 according to the state of each bit of the search data SD. In this embodiment, the search voltage SS1 may be, from the top to the bottom of the figure, the voltage VH, VL, VL, VL, VH, VH, VL in sequence, wherein the voltage VH is greater than the voltage VL, and the voltage VH is between the distribution range of the critical voltages VHT and VLT, and the voltage VL is lower than the distribution range of the critical voltage VLT, as shown in the schematic diagram of the voltage value of the search voltage and the distribution state of the critical voltage of the search memory cell shown in FIG2B. Correspondingly, the search voltage SS2 may be, from the top to the bottom of the figure, the voltage VL, VH, VH, VH, VL, VH, VL, VL, VL.

In this embodiment, when the search data SD is not a don't care and invalid data, the corresponding search voltages SS1 and SS2 are complementary. When the search data SD is a don't care, the corresponding search voltages SS1 and SS2 are both voltages VL, and when the search data SD is invalid data, the corresponding search voltages SS1 and SS2 are both voltages VH. In addition, when the search data SD is a don't care, the corresponding search result must be matched, and when the search data SD is invalid data, the corresponding search result must be inconsistent.

The voltage of the search voltage and the corresponding logical state of the data to be searched can be shown in the following table: Search data Search voltage SS1 Search voltage SS2 0 V L VH 1 VH V L not give a damn about V L V L Invalid data VH VH

When performing a search operation in the memory, when the search memory cell has a critical voltage LVT and receives a search voltage of voltage VH, the search memory cell can be turned on and generate a current, and under other conditions, the search memory cell can be turned off. In detail, when the storage data of the search memory cell pair matches the desired search data SD, both search memory cells in the search memory cell pair are turned off and no current is generated. When the storage data of the search memory cell pair does not match the desired search data SD, at least one of the two search memory cells in the search memory cell pair can be turned on and generate a current.

In this embodiment, search memory cells CA1-CA3 can be turned on and generate current I, and search memory cells CB1-CB4 can be turned on and generate current I. Therefore, sense amplifier SA1 can receive a current equal to 3I on bit lines BLA1 and BLB1; sense amplifier SA2 can receive a current equal to 1I on bit lines BLA2 and BLB2; and sense amplifier SA3 can receive a current equal to 2I on bit lines BLA3 and BLB3. The sense amplifiers SA1~SA3 can generate search results R1~R3 respectively, wherein the search result R1 represents the similarity between the stored data in the search memory cells on the bit lines BLA1 and BLB1 and the desired search data SD, which is the same as the similarity between the stored data in the search memory cells on the bit lines BLA3 and BLB3 and the desired search data SD (lower than the similarity of the search result R2); the search result R2 represents the highest similarity between the stored data in the search memory cells on the bit lines BLA2 and BLB2 and the desired search data SD. In other words, the similarity between the stored data in the search memory cells and the desired search data SD is negatively correlated with the current provided on the bit lines.

Please refer to FIG. 3A and FIG. 3B , which are schematic diagrams showing another implementation of the memory search action of the embodiment of the present invention. In FIG. 3B , the memory device 300 includes memory cell blocks 310 and 320. The memory cell block 310 has bit lines BLA1 to BLA3, and a plurality of search memory cells are coupled to each of the bit lines BLA1 to BLA3. The memory cell block 320 has bit lines BLB1 to BLB3, and a plurality of search memory cells are coupled to each of the bit lines BLB1 to BLB3. The multiple search memory cells in the memory cell block 310 are paired with the multiple search memory cells in the memory cell block 320 to form a search memory cell pair. The pairing method has been described in detail in the embodiment of FIG. 1 and will not be described in detail here.

When the storage data of the search memory cell pair is multi-bit data, multiple voltages can be set to correspond to multiple possible logical values of the storage data. And corresponding to the storage data stored in the search memory cell pair, the critical voltage of the first search memory cell in the search memory cell pair is set to one of the multiple voltages, and the critical voltage of the second search memory cell in the search memory cell pair is set to another of the multiple voltages.

In detail, the above-mentioned multiple voltages may be a first voltage to an Nth voltage, wherein the first voltage to the Nth voltage may be arranged in order from small to large. In this embodiment, the critical voltage of the first search memory cell and the critical voltage of the second search memory cell may be complementary, and may be shown in the following table: Save data First search for critical voltage of memory cells Second search for the critical voltage of memory cells 0 Vt0 Vt7 1 Vt1 Vt6 2 Vt2 Vt5 3 Vt3 Vt4 4 Vt4 Vt3 5 Vt5 Vt2 6 Vt6 Vt1 7 Vt7 Vt0 In the above table, N is taken as an example to be equal to 8. The first voltage to the eighth voltage are critical voltages Vt0 to Vt7, respectively, wherein the critical voltages Vt0 < Vt1 < Vt2 < … < Vt7.

On the other hand, corresponding to multiple possible logic values of the data to be searched, the first search voltage applied to the memory cell block 310 may be one of the first setting voltage to the Nth setting voltage, and the second search voltage applied to the memory cell block 320 may be another of the first setting voltage to the Nth setting voltage. The first setting voltage to the Nth setting voltage may be arranged in order from small to large. In this embodiment, corresponding to the same logic value of the data to be searched, the first search voltage and the second search voltage may be complementary, and may be shown in the following table: Search data First search voltage Second search voltage 0 V0 V7 1 V1 V6 2 V2 V5 3 V3 V4 4 V4 V3 5 V5 V2 6 V6 V1 7 V7 V0 In the above table, N is taken as an example to be 8. The first search voltage to the eighth search voltage are set voltages V0 to V7, respectively, wherein the set voltages V0 < V1 < V2 < … < V7.

In FIG3A, the critical voltage Vtx of the search memory cell, the received search voltage Vx~Vx+7, and the current size that the search memory cell can generate are shown. Taking x=0 as an example, when the search memory cell has a critical voltage Vt0 and the received search voltage is a set voltage V0~Vx, the search memory cell can generate currents I0, I0, I1, I2, I3, I4, I5, I6, and I7, respectively, where the current I0 is substantially equal to 0.

It is worth mentioning that FIG. 3A only illustrates the transfer characteristic curve of the search memory cell, and does not mean that all the search voltages Vx~Vx+7 in FIG. 3A need to be generated when performing the search operation in the memory.

In FIG3B , the search memory cell pair on the bit lines BLA1 and BLB1 store storage data of logic values 0, 1, 2, 3, 4, 5, 6, and 7 in order from the top to the bottom of FIG3B . Therefore, the search memory cell on the bit line BLA1 has critical voltages Vt0, Vt1, Vt2, Vt3, Vt4, Vt5, Vt6, and Vt7 in order from the top to the bottom of FIG3B . The search memory cell on the bit line BLB1 has critical voltages Vt7, Vt6, Vt5, Vt4, Vt3, Vt2, Vt1, and Vt0 in order from the top to the bottom of FIG3B .

The search memory cell pair on the bit lines BLA2 and BLB2 stores storage data of logic values 1, 2, 3, 4, 5, 6, 7, and 6 in sequence from the top to the bottom of FIG. 3B . Therefore, the search memory cell on the bit line BLA2 has critical voltages Vt1, Vt2, Vt3, Vt4, Vt5, Vt6, Vt7, and Vt6 in sequence from the top to the bottom of FIG. 3B . The search memory cell on the bit line BLB2 has critical voltages Vt6, Vt5, Vt4, Vt3, Vt2, Vt1, Vt0, and Vt1 in sequence from the top to the bottom of FIG. 3B .

In addition, the search memory cell pair on the bit lines BLA3 and BLB3 stores storage data of logic values 7, 6, 5, 4, 3, 2, 1, and 0, respectively, from the top to the bottom of FIG. 3B. Therefore, the search memory cell on the bit line BLA3 has critical voltages Vt7, Vt6, Vt5, Vt4, Vt3, Vt2, Vt1, and Vt0, from the top to the bottom of FIG. 3B. The search memory cell on the bit line BLB3 has critical voltages Vt0, Vt1, Vt2, Vt3, Vt4, Vt5, Vt6, and Vt7, from the top to the bottom of FIG. 3B.

On the other hand, the logical values of the search data SD may be 0, 1, 2, 3, 4, 5, 6, and 7, from the top to the bottom of FIG. 3B . The search voltage SS1 generated by the corresponding search voltage SD may be search voltages V0, V1, V2, V3, V4, V5, V6, and V7, from the top to the bottom of FIG. 3B . The search voltage SS2 may be search voltages V7, V6, V5, V4, V3, V2, V1, and V0, from the top to the bottom of FIG. 3B .

According to the transfer characteristic curve corresponding to FIG. 3A , in the embodiment of FIG. 3B , in the memory cell block 310 , the search memory cell CA1 can generate a current I1; the search memory cell CA2 can generate a current I1; the search memory cell CA3 can generate a current I3; the search memory cell CA4 can generate a current I5; and the search memory cell CA5 can generate a current I7. In the memory cell block 320 , each of the search memory cells CB1 to CB7 and CB11 can generate a current I1; the search memory cell CB10 can generate a current I3; the search memory cell CB9 can generate a current I5; and the search memory cell CB8 can generate a current I7. The remaining search memory cells may be turned off and provide a current approaching zero (eg, current I0).

Sense amplifier SA1 can receive the current on bit lines BLA1 and BLB1 (approaching 0); sense amplifier SA2 can receive the current on bit lines BLA2 and BLB2 (=8*I1); sense amplifier SA3 can receive the current on bit lines BLA3 and BLB3 (=2*I1+2*I5+2*I7). In this way, the similarity indicated by the search result R1 generated by sense amplifier SA1 is higher than the similarity indicated by the search result R2 generated by sense amplifier SA2. The similarity indicated by the search result R2 generated by sense amplifier SA2 is higher than the similarity indicated by the search result R3 generated by sense amplifier SA3.

Please refer to FIG. 4A and FIG. 4B , which are schematic diagrams showing another implementation of the memory search action of the embodiment of the present invention. In FIG. 4B , the memory device 400 includes memory cell blocks 410 and 420. The memory cell block 410 has bit lines BLA1 to BLA3, and a plurality of search memory cells are coupled to each of the bit lines BLA1 to BLA3. The memory cell block 420 has bit lines BLB1 to BLB3, and a plurality of search memory cells are coupled to each of the bit lines BLB1 to BLB3. The multiple search memory cells in the memory cell block 410 are paired with the multiple search memory cells in the memory cell block 420 to form a search memory cell pair. The pairing method has been described in detail in the embodiment of FIG. 1 and will not be described in detail here.

In FIG4A , transfer characteristic curve 401 is a transfer characteristic curve of a first search memory cell in a memory cell block 410, and transfer characteristic curve 402 is a transfer characteristic curve of a second search memory cell in a memory cell block 420. In FIG4A , transfer characteristic curve 401 corresponds to a dotted horizontal axis, and transfer characteristic curve 402 corresponds to a solid horizontal axis. The vertical axis is the current IA generated by the first search memory cell or the current IB generated by the second search memory cell. In this embodiment, the search memory cell pair is used to store analog storage data. The first search memory cell and the second search memory cell can be changed between a minimum voltage Vm and a maximum voltage VM respectively according to corresponding storage data.

Regarding the setting of the search voltage, the first search voltage VA provided to the memory cell block 410 can be generated according to the desired search data, and the second search voltage VB provided to the memory cell block 420 can be equal to the sum of the minimum voltage Vm and the maximum voltage VM, minus the first search voltage VA (VB = Vm + VM - VA).

In this embodiment, when the search voltage VA' is in the cut-off region of the search memory cell, the search memory cell does not generate current and indicates that the search result is consistent. When the search voltage VA'' is not in the cut-off region of the search memory cell, at least one search memory cell in the search memory cell pair may generate current and indicates that the search result is inconsistent.

In FIG4B , the critical voltages of the multiple search memory cells in the memory cell block 410 can be adjusted accordingly according to the stored data and have the characteristics of the transfer characteristic curve TC1. The critical voltages of the multiple search memory cells in the memory cell block 420 can also be adjusted accordingly according to the stored data and have the characteristics of the transfer characteristic curve TC2.

Corresponding to the search data, the search voltage SS1 can be equal to the voltages VA1 to VA8 from the top to the bottom of FIG. 4B. The search voltage SS2 can be calculated from the voltages VA1 to VA8, the maximum voltage VM, and the minimum voltage Vm from the top to the bottom of FIG. 4B, and can be equal to the voltages VB1 to VB8 in sequence. It is worth noting that when the first search voltage is large enough, the second search voltage is at least equal to the minimum voltage Vm; and when the first search voltage is small enough, the second search voltage is at most equal to the maximum voltage VM.

The sense amplifier SA1 is coupled to the bit lines BLA1 and BLB1, the sense amplifier SA2 is coupled to the bit lines BLA2 and BLB2, and the sense amplifier SA3 is coupled to the bit lines BLA3 and BLB3. The sense amplifiers SA1 to SA3 generate search results R1, R2, and R3 according to the currents on the coupled bit lines BLA1, BLB1, BLA2, BLB2, BLA3, and BLB3, respectively. The similarities indicated by the search results R1, R2, and R3 are negatively correlated with the currents received by the sense amplifiers SA1 to SA3 on the bit lines BLA1, BLB1, BLA2, BLB2, BLA3, and BLB3, respectively.

Please refer to FIG. 5 , which is a schematic diagram of a memory device of another embodiment of the present invention. The memory device 500 is used to perform an internal search operation. The memory device 500 has memory cell blocks 510 and 520. The memory cell block 110 includes a plurality of search memory cells CA1 to CA8, and the memory cell block 120 includes a plurality of search memory cells CB1 to CB8. Among them, the search memory cells CA1 to CA4 are coupled to the same bit line BLA1, and the search memory cells CA5 to CA8 are coupled to the same bit line BLA2. Search memory cells CA1 and CA5 are coupled to the same word line WLA1; search memory cells CA2 and CA6 are coupled to the same word line WLA2; search memory cells CA3 and CA7 are coupled to the same word line WLA3; search memory cells CA4 and CA8 are coupled to the same word line WLA4. Search memory cells CA1, CA2, CA3, and CA4 share the same source line SLA1, and search memory cells CA5, CA6, CA7, and CA8 share the same source line SLA2.

In addition, search memory cells CB1-CB4 are coupled to the same bit line BLB1, and search memory cells CB5-CB8 are coupled to the same bit line BLB2. Search memory cells CB1 and CB5 are coupled to the same word line WLB1; search memory cells CB2 and CB6 are coupled to the same word line WLB2; search memory cells CB3 and CB7 are coupled to the same word line WLB3; search memory cells CB4 and CB8 are coupled to the same word line WLB4. Search memory cells CB1, CB2, CB3, and CB4 share the same source line SLB1, and search memory cells CB5, CB6, CB7, and CB8 share the same source line SLB2.

In this embodiment, the memory device 500 may be a flash memory.

Please refer to FIG. 6 below, which is a flow chart of an in-memory search method according to an embodiment of the present invention. In step S610, a first search memory cell and a second search memory cell are respectively set in a first memory cell block and a second memory cell block. In step S620, the first search memory cell and the second search memory cell form a search memory cell pair, wherein the first search memory cell and the second search memory cell respectively receive a first search voltage and a second search voltage, and the second search voltage is generated according to the desired search data. In step S630, a sense amplifier is provided to generate a search result according to the signals provided by the first search memory cell and the second search memory cell respectively through the first bit line and the second bit line.

The implementation details of the above steps have been described in detail in the aforementioned embodiments and implementation methods, and will not be elaborated here.

In summary, the present invention forms a search memory cell pair by using two search memory cells in different memory cell blocks, and uses a search memory cell pair to store a storage data. In this way, when a search action is performed, all word lines in a memory cell block can receive a search voltage generated according to the data to be searched. In other words, in a search action, the length of the search data that can be provided by the memory device of the present invention can be increased, effectively improving the efficiency of the search action in the memory.

100, 200, 300, 400, 500: memory device 110, 120, 210, 220, 310, 320, 410, 420, 510, 520: memory cell block 401, 402, TC1, TC2: transfer characteristic curve BLA1~BLA3, BLB1~BLB3: bit line CA1~CA8, CB1~CB11: search memory cell I, I1~I7, IA, IB: current LVT, HVT, Vt0~Vt7, Vtx: critical voltage R1~R3: search result S610~S630: step SA1~SA3: sense amplifier SD: data to be searched SLA1, SLA2, SLB1, SLB2: source line SS1, SS2, Vx~Vx+7, VA, VB, VA’, VA’’: search voltage V0~V7: set voltage VA1~VA8, VB1~VB8, VH, VL: voltage VM: maximum voltage Vm: minimum voltage WLA1~WLA4, WLB1~WLB4: word line

FIG. 1 is a schematic diagram of a memory device of an embodiment of the present invention. FIG. 2A is a schematic diagram of an embodiment of a memory search action of the present invention. FIG. 2B is a schematic diagram of the voltage value of the search voltage and the distribution state of the critical voltage of the search memory cell. FIG. 3A and FIG. 3B are schematic diagrams of another embodiment of the memory search action of the present invention. FIG. 4A and FIG. 4B are schematic diagrams of another embodiment of the memory search action of the present invention. FIG. 5 is a schematic diagram of a memory device of another embodiment of the present invention. FIG. 6 is a flow chart of the memory search method of an embodiment of the present invention.

100: Memory device

110, 120: memory cell blocks

BLA1, BLA2, BLB1, BLB2: bit lines

CA1~CA8, CB1~CB8: Searching for memory cells

R1, R2: Search results

SA1, SA2: sensor amplifier

SLA1, SLA2, SLB1, SLB2: source line

WLA1~WLA4, WLB1~WLB4: character line

Claims (20)

A memory device for performing a search operation in a memory includes: a first memory cell block; a second memory cell block; and at least one search memory cell pair, including a first search memory cell and a second search memory cell, wherein the first search memory cell and the second search memory cell are respectively arranged in the first memory cell block and the second memory cell block, and the first search memory cell and the second search memory cell are respectively arranged in the first memory cell block and the second memory cell block. The memory cell receives a first search voltage and a second search voltage respectively, wherein the first search voltage and the second search voltage are generated according to a desired search data; and a sense amplifier is coupled to the first search memory cell and the second search memory cell respectively through a first bit line and a second bit line, and generates a search result according to the signals on the first bit line and the second bit line. A memory device as described in claim 1, wherein when the storage data of the at least one search memory cell pair is single-bit data, the logical values of the first search voltage and the second search voltage complement each other, and when the storage data is a first logical value, the first search memory cell has a first critical voltage, the second search memory cell has a second critical voltage, and the first critical voltage is different from the second critical voltage. A memory device as described in claim 2, wherein when the stored data of the at least one search memory cell pair is don't care, the first search memory cell and the second search memory cell both have the first critical voltage, wherein the first critical voltage is greater than the second critical voltage. The memory device as described in claim 3, wherein when the stored data of the at least one search memory cell pair is invalid data, the first search memory cell and the second search memory cell both have the second critical voltage. A memory device as described in claim 2, wherein when the stored data of the at least one search memory cell pair matches the desired search data, the first search memory cell and the second search memory cell are both turned off, and when the stored data of the at least one search memory cell pair does not match the desired search data, at least one of the first search memory cell and the second search memory cell is turned on. A memory device as described in claim 1, wherein when the storage data of the at least one search memory cell pair is multi-bit data, corresponding to the logical value of the storage data, the critical voltage of the first search memory cell is one of a first voltage to an Nth voltage, and the critical voltage of the second search memory cell is another of the first voltage to the Nth voltage, wherein the first voltage to the Nth voltage are arranged in order from small to large. A memory device as described in claim 5, wherein corresponding to the multiple logical values of the data to be searched, the first search voltage is one of a first setting voltage to an Nth setting voltage, and the second search voltage is another of the first setting voltage to the Nth setting voltage. A memory device as described in claim 5, wherein when the stored data of the at least one search memory cell pair matches the data to be searched, the first search memory cell and the second search memory cell are both turned off, and when the stored data of the at least one search memory cell pair does not match the data to be searched, the first search memory cell and the second search memory cell determine whether to generate a first current and a second current respectively according to the similarity between the stored data and the data to be searched. A memory device as described in claim 1, wherein when the storage data of the at least one search memory cell pair is analog data, the critical voltages of the first search memory cell and the second search memory cell are adjusted between a maximum voltage and a minimum voltage according to the storage data, the first search voltage is generated according to the desired search data, and the second search voltage is equal to the sum of the maximum voltage and the minimum voltage minus the first search voltage. A memory device as described in claim 9, wherein the first search memory cell and the second search memory cell provide a first current and a second current respectively according to the similarity between the stored data and the data to be searched, and the magnitude of the first current and the second current are negatively correlated with the similarity between the stored data and the data to be searched. A method for searching in memory includes: respectively setting a first search memory cell and a second search memory cell in a first memory cell block and a second memory cell block; making the first search memory cell and the second search memory cell form a search memory cell pair, wherein the first search memory cell and the second search memory cell respectively receive a first search voltage and a second search voltage, the first search voltage and the second search voltage are generated according to a desired search data; and providing a sense amplifier to generate a search result according to the signals provided by the first search memory cell and the second search memory cell respectively through a first bit line and a second bit line. The in-memory search method as described in claim 11, wherein when the storage data of the at least one search memory cell pair is single-bit data, the logical values of the first search voltage and the second search voltage complement each other, and when the storage data is a first logical value, the first search memory cell has a first critical voltage, the second search memory cell has a second critical voltage, and the first critical voltage is different from the second critical voltage. The in-memory search method as described in claim 12, wherein when the stored data of the at least one search memory cell pair is don't care, the first search memory cell and the second search memory cell both have the first critical voltage, wherein the first critical voltage is greater than the second critical voltage. In the in-memory search method as described in claim 13, when the stored data of at least one search memory cell pair is invalid data, both the first search memory cell and the second search memory cell have the second critical voltage. The in-memory search method as described in claim 12, wherein when the stored data of the at least one search memory cell pair matches the desired search data, the first search memory cell and the second search memory cell are both turned off, and when the stored data of the at least one search memory cell pair does not match the desired search data, at least one of the first search memory cell and the second search memory cell is turned on. The in-memory search method as described in claim 11, wherein when the storage data of the at least one search memory cell pair is multi-bit data, corresponding to the logical value of the storage data, the critical voltage of the first search memory cell is one of a first voltage to an Nth voltage, and the critical voltage of the second search memory cell is another of the first voltage to the Nth voltage, wherein the first voltage to the Nth voltage are arranged in order from small to large. The in-memory search method as described in claim 15, wherein the first search voltage is one of a first setting voltage to an Nth setting voltage, and the second search voltage is another of the first setting voltage to the Nth setting voltage. The in-memory search method as described in claim 15, wherein when the stored data of the at least one search memory cell pair matches the data to be searched, the first search memory cell and the second search memory cell are both turned off; and when the stored data of the at least one search memory cell pair does not match the data to be searched, the first search memory cell and the second search memory cell are made to determine whether to generate a first current and a second current respectively according to the similarity between the stored data and the data to be searched. The in-memory search method as described in claim 11, wherein when the storage data of the at least one search memory cell pair is analog data, the critical voltage of the first search memory cell and the second search memory cell is adjusted between a maximum voltage and a minimum voltage according to the storage data; and the first search voltage is generated according to the data to be searched, and the second search voltage is equal to the sum of the maximum voltage and the minimum voltage minus the first search voltage. The in-memory search method as described in claim 19 further includes: enabling the first search memory cell and the second search memory cell to provide a first current and a second current respectively according to the similarity between the stored data and the data to be searched, wherein the magnitude of the first current and the second current is negatively correlated with the similarity between the stored data and the data to be searched.

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