Claims
- 1. A method for designing a limited function look-up table having a reduced number of programmable architecture elements, the look-up table having a plurality of inputs, the method comprising:
- choosing a plurality of logic functions to be performed by the look-up table;
- determining an output state for each set of input variables, each output state comprising an array of responses of the plurality of logic functions to a particular set of input variables;
- forming groups of the output states, the groups of output states comprising identical output states;
- eliminating selected groups of the output states, the selected groups not requiring programmable architecture elements; and
- assigning a programmable architecture element for each remaining group of output states, each programmable architecture element being for storing the responses of a particular output state.
- 2. A method as described in claim 1 wherein the programmable architecture elements comprise memory cells.
- 3. A method as described in claim 1 wherein the programmable architecture elements comprise static random-access-memory cells.
- 4. A method as described in claim 1 wherein the logic functions comprise AND, OR and XOR.
- 5. A look-up table architecture for performing a limited number of specific logic functions with a first number of input variables, said look-up table architecture comprising:
- a look-up table output terminal;
- a second number of programmable architecture elements, the programmable architecture elements for storing outputs, the outputs being organized into output states, each output state comprising responses of the specific logic functions to a particular set of input variables, the second number being less than a third number of programmable architecture elements required for implementing a look-up table architecture capable of performing all possible logic functions of the first number of variables, each programmable architecture element being for storing the outputs of a particular output state;
- a plurality of logic gates coupled to the programmable architecture elements and the look-up table output terminal, the logic gates for gating the outputs stored in the programmable architecture elements to the look-up table output terminal; and
- a plurality of input terminals connected to the logic gates, signals being supplied to the input terminals, the signals defining an input state to control the plurality of logic gates, thereby facilitating the gating of an output stored in a particular programmable architecture element to the output terminal.
- 6. A look-up table architecture as described in claim 5 further comprising a plurality of inverters, the inverters for generating complements of the input states, the complements for controlling the logic gates.
- 7. A look-up table architecture as described in claim 5 wherein the programmable architecture elements comprise memory cells.
- 8. A look-up table architecture as described in claim 5 wherein the programmable architecture elements comprise static random-access-memory cells.
- 9. A look-up table architecture for performing AND, OR, and XOR logic functions, the look-up table architecture comprising:
- a look-up table output terminal;
- no more than four programmable architecture elements, the programmable architecture elements for storing outputs, the outputs being organized into output states, each output state comprising responses of the AND, OR, and XOR logic functions to a particular set of input variables, each programmable architecture element being for storing the outputs of a particular output state;
- a plurality of logic gates coupled to the programmable architecture elements and the look-up table output terminal, the logic gates for gating the outputs stored in the programmable architecture elements to the look-up table output terminal; and
- at least three input terminals connected to the logic gates, signals being supplied to the input terminals, the signals defining an input state to control the plurality of logic gates, thereby facilitating the gating of an output stored in a particular programmable architecture element to the output terminal.
- 10. A look-up table architecture as described in claim 9 further comprising a plurality of inverters, the inverters for generating complements of the input states, the complements for controlling the logic gates.
- 11. A look-up table architecture as described in claim 9 wherein the programmable architecture elements comprise memory cells.
- 12. A look-up table architecture as described in claim 9 wherein the programmable architecture elements comprise static random-access-memory cells.
- 13. A look-up table architecture for performing AND, OR, and XOR logic functions, the look-up table architecture comprising:
- a look-up table output terminal;
- no more than four programmable static random-access-memory cells, the static random-access-memory cells for storing outputs, the outputs being organized into output states, each output state comprising responses of the AND, OR, and XOR logic functions to a particular set of input variables, each static random-access-memory cell being for storing the outputs of a particular output state;
- a plurality of AND and OR logic gates coupled to the static random-access-memory cells and the look-up table output terminal, the logic gates for gating the outputs stored in the static random-access-memory cells to the look-up table output terminal;
- at least three input terminals connected to the logic gates, signals being supplied to the input terminals, the signals defining an input state to control the plurality of logic gates, thereby facilitating the gating of an output stored in a particular static random-access-memory cell to the output terminal; and
- a plurality of inverters, the inverters for generating complements of the input states, the complements for controlling the logic gates.
Parent Case Info
This is a Continuation of application Ser. No. 08/017,096, filed Feb. 12, 1993, now abandoned.
US Referenced Citations (6)
Non-Patent Literature Citations (1)
Entry |
Altera Corporation 1992 Data Book, pp. 1-34. |
Continuations (1)
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Number |
Date |
Country |
Parent |
017096 |
Feb 1993 |
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