Multiport semiconductor memory device
First Claim
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1. A semiconductor memory device comprising:
- a memory array having a plurality of memory cells arranged in rows and columns;
first and second ports receiving and transmitting input/output signals independent of each other; and
a selection circuit capable of simultaneously accessing said memory array according to addresses respectively input to said first and second ports, said memory array including a plurality of first and second word lines provided respectively corresponding to memory cell rows, and a plurality of first and second bit lines provided respectively corresponding to memory cell columns, each of said memory cells including a flip-flop circuit for setting first and second storage nodes to one and the other of first and second potential levels, respectively, according to data to be stored, a first gate transistor having its gate electrically coupled to a corresponding first word line for electrically coupling a corresponding first bit line to said flip-flop circuit, and a second gate transistor having its gate electrically coupled to a corresponding second word line for electrically coupling a corresponding second bit line to said flip-flop circuit, said selection circuit including first and second row decoders provided respectively corresponding to said first and second ports for outputting respective row selection instructions according to input addresses, and a plurality of word drivers provided respectively corresponding to memory cell rows, each for driving corresponding first and second word lines according to row selection results from said first and second row decoders, wherein when receiving an input of a row selection instruction from one of said first and second row decoders, each of said word drivers sets a voltage level of a word line corresponding to the one to a first voltage level, and when receiving inputs of row selection instructions from both of said first and second row decoders, each of said word drivers sets respective voltage levels of first and second word lines to a second voltage level lower than said first voltage level.
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Abstract
In the same row access, a voltage level of word lines WLA and WLB is set to a power supply voltage VDD−Vtp. On the other hand, in different rows access, a voltage level of word line WLA or WLB is set to power supply voltage VDD. Therefore, when both ports PA and PB simultaneously access the same row, the voltage level of word lines WLA, WLB is set to power supply voltage VDD−Vtp. Thus, a driving current amount of a memory cell is reduced, thereby preventing a reduction in a current ratio of a transistor. As a result, deterioration of SNM can be prevented.
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Citations
8 Claims
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1. A semiconductor memory device comprising:
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a memory array having a plurality of memory cells arranged in rows and columns;
first and second ports receiving and transmitting input/output signals independent of each other; and
a selection circuit capable of simultaneously accessing said memory array according to addresses respectively input to said first and second ports, said memory array including a plurality of first and second word lines provided respectively corresponding to memory cell rows, and a plurality of first and second bit lines provided respectively corresponding to memory cell columns, each of said memory cells including a flip-flop circuit for setting first and second storage nodes to one and the other of first and second potential levels, respectively, according to data to be stored, a first gate transistor having its gate electrically coupled to a corresponding first word line for electrically coupling a corresponding first bit line to said flip-flop circuit, and a second gate transistor having its gate electrically coupled to a corresponding second word line for electrically coupling a corresponding second bit line to said flip-flop circuit, said selection circuit including first and second row decoders provided respectively corresponding to said first and second ports for outputting respective row selection instructions according to input addresses, and a plurality of word drivers provided respectively corresponding to memory cell rows, each for driving corresponding first and second word lines according to row selection results from said first and second row decoders, wherein when receiving an input of a row selection instruction from one of said first and second row decoders, each of said word drivers sets a voltage level of a word line corresponding to the one to a first voltage level, and when receiving inputs of row selection instructions from both of said first and second row decoders, each of said word drivers sets respective voltage levels of first and second word lines to a second voltage level lower than said first voltage level. - View Dependent Claims (2)
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3. A semiconductor memory device comprising:
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a memory array having a plurality of memory cells arranged in rows and columns;
first and second ports receiving and transmitting input/output signals independent of each other; and
a selection circuit capable of simultaneously accessing said memory array according to addresses respectively input to said first and second ports, said memory array including a plurality of first and second word lines provided respectively corresponding to memory cell rows, and a plurality of first and second bit lines provided respectively corresponding to memory cell columns, each of said memory cells including a flip-flop circuit for setting first and second storage nodes to one and the other of first and second potential levels, respectively, according to data to be stored, a first gate transistor having its gate electrically coupled to a corresponding first word line for electrically coupling a corresponding first bit line to said flip-flop circuit, and a second gate transistor having its gate electrically coupled to a corresponding second word line for electrically coupling a corresponding second bit line to said flip-flop circuit, said semiconductor memory device further comprising power supply lines provided respectively corresponding to memory cell rows, each supplying an operating voltage to said flip-flop circuit of each memory cell included in a corresponding memory cell row, said selection circuit including first and second row decoders provided respectively corresponding to said first and second ports for outputting respective row selection instructions according to input addresses, and a plurality of word drivers provided respectively corresponding to memory cell rows, each driving corresponding first and second word lines according to row selection results from said first and second row decoders and also driving a corresponding power supply line, wherein each of said word drivers sets a voltage level of a corresponding power supply line to a first voltage level when receiving an input of a row selection instruction from one of said first and second row decoders, and sets a voltage level of said corresponding power supply line to a second voltage level higher than said first voltage level when receiving inputs of row selection instructions from both of said first and second row decoders. - View Dependent Claims (4)
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5. A semiconductor memory device comprising:
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a memory array having a plurality of memory cells arranged in rows and columns;
first and second ports receiving and transmitting input/output signals independent of each other; and
a selection circuit capable of simultaneously accessing said memory array according to addresses respectively input to said first and second ports, said memory array including a plurality of first and second word lines provided respectively corresponding to memory cell rows, and a plurality of first and second bit lines provided respectively corresponding to memory cell columns, each of said memory cells including a flip-flop circuit for setting first and second storage nodes to one and the other of first and second potential levels, respectively, according to data to be stored, a first gate transistor having its gate electrically coupled to a corresponding first word line for electrically coupling a corresponding first bit line to said flip-flop circuit, and a second gate transistor having its gate electrically coupled to a corresponding second word line for electrically coupling a corresponding second bit line to said flip-flop circuit, said selection circuit including first and second row decoders provided respectively corresponding to said first and second ports for outputting respective row selection instructions according to input addresses, and a plurality of word drivers provided respectively corresponding to memory cell rows, each for driving corresponding first and second word lines according to row selection results from said first and second row decoders, wherein when receiving an input of a row selection instruction from one of said first and second row decoders, each of said word drivers drives a word line corresponding to the one, and when receiving inputs of row selection instructions from both of said first and second row decoders, each of said word drivers drives either one of the word lines. - View Dependent Claims (6, 7, 8)
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Specification