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US 6,748,411 B1Granted
Hierarchical carry-select multiple-input split adder
AssigneeAgere Systems Inc.
InventorMohammad Reza Hakami
Life of this patent
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Abstract
An adder or an integrated circuit including an adder, includes a hierarchical carry-select split adder capable of operating in a split mode of operation when a mode select input takes on a first state. It is also capable of operating in a hierarchical carry-select mode of operation when the mode select input takes on a second state.
Claims15
An adder comprising:
- a first adder for receiving as inputs a plurality of operands k in number, k being an integer at least three, and k−1 carry-in inputs, the first adder providing as outputs a sum that is the sum of the k operands and the k−1 carry-in inputs, and k−1 carry-out outputs;
- a plurality of 2k−1−1 carry-select adders, each of the carry-select adders receiving a plurality of operands k in number, each of the carry-select adders having k−1 predetermined carry-in inputs, each of the carry-select adders providing as outputs a sum that is the sum of the k operands and the respective predetermined carry-in inputs;
- a multiplexer for receiving as inputs the sum outputs from the carry-select adders, the multiplexer receiving a select input to select one of the inputs of the multiplexer as an output of the multiplexer;
- a code converter for receiving as inputs a mode select input and the k−1 carry-out outputs from the first adder, the code converter causing the first adder and the carry-select adders to operate as a split adder when the mode select input takes on a first state, and the code converter causing the first adder and the carry-select adders to operate as a hierarchical carry-select adder when the mode select input takes on a second state.
1 more element
An integrated circuit, including an adder comprising:
- a first adder for receiving as inputs a plurality of operands k in number, k being an integer at least three, and k−1 carry-in inputs, the first adder providing as outputs a sum that is the sum of the k operands and the k−1 carry carry-in inputs, and k−1 carry-out outputs;
- a plurality of 2k−1−1 carry-select adders, each of the carry-select adders receiving a plurality of operands k in number, each of the carry-select adders having k−1 predetermined carry-in inputs, each of the carry-select adders providing as outputs a sum that is the sum of the k operands and the respective predetermined carry-in inputs;
- a multiplexer for receiving as inputs the sum outputs from the carry-select adders, the multiplexer receiving a select input to select one of the inputs of the multiplexer as an output of the multiplexer;
- a code converter for receiving as inputs a mode select input and the k−1 carry-out outputs from the first adder, the code converter causing the first adder and the carry-select adders to operate as a split adder when the mode select input takes on a first state, and the code converter causing the first adder and the carry-select adders to operate as a hierarchical carry-select adder when the mode select input takes on a second state.
1 more element
An adder, comprising:
- a first adder module having a first input and a first output;
- a plurality of carry-select adders in parallel with said first adder module, said plurality of carry-select adders;
- and
- a code converter having a mode select input, the code converter in a first state causing the first adder and the carry-select adders to operate as a split adder, and in a second state causing the plurality of carry-select adders to operate as a carry-select adder;
- wherein said adder is capable of accommodating more than two operands as inputs.
2 more elements
Dependencies are inferred from the claim text.