FPGA having low power, fast carry chain
First Claim
1. A field programmable gate array (FPGA), comprising:
- carry logic unit having a logic portion configured to execute a carry bit generating operation, the carry logic unit comprising an empowerment portion having a power voltage supplying terminal and a power sinking terminal, the empowerment portion being structured to support flow therethrough of an empowering current flowing through and empowering the carry bit generating operations of the logic portion of the carry logic unit when said carry bit generating operations are active, the empowering current flowing from the power voltage supplying terminal to the power sinking terminal;
wherein the empowerment portion of the carry logic unit includes a unit empowering/depowering switching transistor connected to the power sinking terminal of the carry logic unit and structured and disposed so as to support flow of the empowering current through the switching transistor; and
a programmable, empowerment/depowerment control signal provider connected to a gate terminal of the switching transistor and programmably configurable to provide depowering control signal to the gate terminal which causes the empowering/depowering switching transistor to interrupt the flow of the empowering current through the logic portion of the carry logic unit such that flow of leakage current through the logic portion is disabled when the flow of the empowering current is interrupted in response to provision of the depowering control signal to the gate terminal.
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Accused Products
Abstract
An in-FPGA carry chain is provided that does not exhibit significant leakage current. In particular, parts of the carry chain can be switched on/off when desired. In this manner, carry chain parts can have their leakage currents substantially disabled when they are not in use, thus saving power. Additionally, there is provided a carry chain whose logic is separate from the other parts (e.g., LUTs) of the logic blocks that perform the remaining arithmetic functions, and whose inputs are the input data to be added, rather than data that is output in delayed fashion from the other parts (e.g., LUTs) of the logic blocks. Such a configuration reduces latency by allowing the carry chain to operate directly on the received input data without need to wait on results from the other parts (e.g., LUTs) of the logic blocks.
14 Citations
18 Claims
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1. A field programmable gate array (FPGA), comprising:
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carry logic unit having a logic portion configured to execute a carry bit generating operation, the carry logic unit comprising an empowerment portion having a power voltage supplying terminal and a power sinking terminal, the empowerment portion being structured to support flow therethrough of an empowering current flowing through and empowering the carry bit generating operations of the logic portion of the carry logic unit when said carry bit generating operations are active, the empowering current flowing from the power voltage supplying terminal to the power sinking terminal; wherein the empowerment portion of the carry logic unit includes a unit empowering/depowering switching transistor connected to the power sinking terminal of the carry logic unit and structured and disposed so as to support flow of the empowering current through the switching transistor; and a programmable, empowerment/depowerment control signal provider connected to a gate terminal of the switching transistor and programmably configurable to provide depowering control signal to the gate terminal which causes the empowering/depowering switching transistor to interrupt the flow of the empowering current through the logic portion of the carry logic unit such that flow of leakage current through the logic portion is disabled when the flow of the empowering current is interrupted in response to provision of the depowering control signal to the gate terminal. - View Dependent Claims (2, 3)
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4. A field programmable gate array (FPGA) having a plurality of configurable logic blocks (CLBs) each comprising:
- a lookup table (LUT) having first and second data input terminals connected to receive respective first and second data signals transmitted thereto as inputs usable by a lookup function implemented in the LUT, and an output terminal for outputting a LUT result signal that is generated by the LUT based on the implemented lookup function of the LUT; and
carry logic unit configured to perform carry bit generating operations that produce carry bits corresponding to carry input signals received by the carry logic unit, the carry logic unit having first, second and third carry logic input terminals for receiving the carry input signals and a carry output terminal for outputting the produced carry bits;
wherein the first and second carry logic input terminals of the carry logic unit are connected respectively to the first and second data input terminals of the lookup table, wherein the plurality of configurable logic blocks (CLBs) includes a first CLB and a second CLB;
wherein the respective lookup tables of the CLBs each includes a respective third data input terminal connected to receive respective third data signal transmitted thereto as an input usable by the respective lookup function implemented in the corresponding LUT of the respective CLB; and
wherein the carry output terminal of the carry logic unit of the first CLB is programmably connectable to the third input terminal of the lookup table of the second CLB. - View Dependent Claims (5, 6, 7)
- a lookup table (LUT) having first and second data input terminals connected to receive respective first and second data signals transmitted thereto as inputs usable by a lookup function implemented in the LUT, and an output terminal for outputting a LUT result signal that is generated by the LUT based on the implemented lookup function of the LUT; and
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8. A field programmable gate array (FPGA) circuit comprising:
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a plurality of programmable lookup tables (LUTs) each having a respective LUT output terminal and respective first, second and third LUT input terminals disposed for receiving corresponding first, second and third LUT input term signals of the respective LUT; a carry bits generating chain having a plurality of carry bit generating units, each carry bit generating unit being associated with one of the LUTs and each carry bit generating unit having a respective unit output terminal and respective first, second and third carry unit input terminals disposed for receiving corresponding first, second and third carry input term signals of the respective carry bit generating unit, where the third carry unit input terminal of each carry bit generating unit in a continuous portion of the chain is connected to the unit output terminal of the previous unit in the chain, wherein the first and second carry unit input terminals of each unit are coupled to receive same respective first and second input signals as corresponding first and second LUT input terminals of the associated LUT, and wherein each carry bit generating unit includes a power cut off circuit configured to selectively cut off power consumption of a carry bit generating logic portion of the unit in response to a received depowering control signal, which depowering control signal is indicative of the respective carry bit generating unit not being used for carry bit generation. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A field programmable gate array (FPGA) circuit comprising:
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a plurality of programmable lookup tables (LUTs) each having a respective LUT output terminal and respective plurality of LUT input terminals disposed for receiving corresponding one of plural LUT input term signals of the respective LUT; a carry bits generating chain having a plurality of carry bit generating units, each carry bit generating unit being associated with one of the LUTs and each carry bit generating unit having a respective unit output terminal and respective first, second and third carry unit input terminals disposed for receiving corresponding first, second and third carry input term signals of the respective carry bit generating unit, where the third carry unit input terminal of each carry bit generating unit in a continuous portion of the chain is connected to the unit output terminal of the previous unit in the chain, wherein each carry bit generating unit includes a power cut off circuit configured to selectively cut off power consumption of a carry bit generating logic portion of the unit in response to a received depowering control signal, which depowering control signal is indicative of the respective carry bit generating unit not being used for carry bit generation. - View Dependent Claims (18)
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Specification