EP0456475A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Programmable logic device
Assignee: Xilinx Inc
•
Filing: 1991-05-08
•
Granted: —
•
Expires: 2011-05-08
Abstract
Abstract Programmable logic devices which include multiple blocks of combinatorial function generators and storage elements, and which are interconnected by a programmable interconnect structure are used, among other things for performing arithmetic functions which use logic for generating the carry function. When a large number of bits is to be processed, the carry function typically causes significant delay or requires significant additional components to achieve a result at high speed. The present invention provides dedicated hardware within the logic blocks for performing the carry function quickly and with a minimum number of components. The invention takes advantage of the fact that a carry signal to be added to two bits can be propagated to the next more significant bit when the two binary bits to be added are unequal, and that one of the bits can serve as the carry signal when the bits are equal.
Inventors
- 👤 Hung-Cheng Hsieh
- 👤 Charles R. Erickson
- 👤 William S. Carter
- 👤 Edmond Y. Cheung
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 12:08
CPC Classifications
G; G06; G06F; G06F7/00; G06F7/38; G06F7/48; G06F7/57; G06F7/50; G06F7/501; G06F7/503; G06F7/505; G06F7/5057
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
135 words
A programmable logic device comprising an array of logic blocks, each logic block having at least one circuit comprising: a first input terminal and a second input terminal; a carry-in terminal and a carry-out terminal; first switching means for connecting the first input terminal to the carry-out terminal; second switching means for connecting the carry-in terminal to the carry-out terminal; means for causing the first switching means to connect the first input terminal to the carry-out terminal when and only when a signal on the first input terminal is equal to a signal on the second input terminal, and for causing the second switching means to connect the carry-in terminal to the carry-out terminal when and only when the signal on the first input terminal does not equal the signal on the second input terminal.
Claim 2
Dependent Claim
79 words
A logic device as claimed in claim 1 wherein the means for causing comprises: an inverter, and an XOR gate with at least two inputs and one output, wherein the first and second input terminals are inputs to the XOR gate; the output of the XOR gate is connected to the input of the inverter; the signal output from the inverter controls the first switching means; and the signal output from the XOR gate controls the second switching means.
Claim 3
Dependent Claim
38 words
A logic device as claimed in claim 1 comprising: means for disconnecting the first input terminal from the carry-out terminal and means for applying an alternative signal to the carry-out terminal when the means for disconnecting is disconnecting.
Claim 4
Dependent Claim
32 words
A logic device as claimed in claim 3 comprising: a third input terminal and means for selecting the alternative signal from a stored value and a signal on the third input terminal.
Claim 5
Dependent Claim
62 words
A logic device as claimed in claim 1 comprising: a third input terminal, means for providing a signal on the third input terminal, and means for selecting between causing the first switching means to connect the first input terminal to the carry-out terminal and causing the first switching means to apply the signal on the third input terminal to the carry-out terminal.
Claim 6
Dependent Claim
30 words
A logic device as claimed in claim 5 comprising means for selecting between applying a stored value to the carry-out terminal and applying an input signal to the carry-out terminal.
Claim 7
Dependent Claim
32 words
A logic device as claimed in claim 1 comprising means for inverting or not inverting a signal to generate an operand, and means for applying the operand to the second input terminal.
Claim 8
Dependent Claim
159 words
A logic device as claimed in claim 1 comprising: an XNOR gate; a first and a second inverter; third and fourth controllable switching means; and a first and a second memory cell, each memory cell having an output and an output-complement; wherein the first and the second input terminals are inputs to the XNOR gate, an output of the XNOR gate is input to the first inverter by the third switching means, the output of the first inverter is input to the second inverter, the output-complement of the first memory cell is input to the first inverter by the fourth switching means, the first switching means is controlled by the output signal of the second inverter, the second switching means is controlled by the output signal of the first inverter, the third switching means is controlled by the output of the second memory cell, and the fourth switching means is controlled by said output-complement of the second memory cell.
Claim 9
Dependent Claim
29 words
A logic device as claimed in claim 8 wherein the memory cells are static random access memory cells, electrically programmable switches, electrically erasable electrically programmable switches, fuses, or antifuses.
Claim 10
Dependent Claim
60 words
A logic device as claimed in claim 1 comprising a three-way multiplexer for selecting between causing the first switching means to connect the first input terminal to the carry-out terminal, causing the first switching means to connect a third input terminal to the carry-out terminal, and causing the first switching means to apply a stored value to the carry-out terminal.
Claim 11
Dependent Claim
104 words
A logic device as claimed in claim 1 comprising: a third input terminal; means for providing a stored value; third, fourth, fifth, and sixth controllable switching means; and means for controlling the third, fourth, fifth and sixth controllable switching means such that: the third input terminal is coupled to the carry-out terminal only when the first, third, and fifth switching means are conductive; the stored value is coupled to the carry-out terminal only when the sixth and the first switching means are conductive; and the first input terminal is coupled to the carry-out terminal only when the fourth and first switching means are conductive.
Claim 12
Dependent Claim
109 words
A logic device as claimed in claim 1 wherein the means for causing comprises: an XNOR gate having two input terminals coupled respectively to the first and second input terminals, and an output terminal; a first inverter, the output of the first inverter controlling the second switching means; means for providing a stored value; third switching means, wherein the third switching means selects between providing the stored value and a signal output from the XNOR gate to the input terminal of the first inverter; and a second inverter connected to the output terminal of the first inverter, the output terminal of the second inverter controlling the first switching means.
Claim 13
Dependent Claim
123 words
A logic device as claimed in claim 1 comprising: an XNOR gate; a first memory cell and second memory cell; a multiplexer with at least two inputs and one output; a third input terminal; wherein the output of the first memory cell is an input of the multiplexer; the third input terminal is an input of the multiplexer; the output of the second memory cell selects between connecting the first memory cell and connecting the third input terminal to the output terminal of the multiplexer; the output of the multiplexer is an input of the XNOR gate; the second input terminal is coupled to an input of the XNOR gate; the XNOR gate and the first input terminal control the means for causing.
Claim 14
Dependent Claim
96 words
A logic device as claimed in claim 1 wherein each logic block has at least: a first circuit and a second circuit, the carry-out terminal of the first circuit being connected to the carry-in terminal of the second circuit, the carry-out terminal of the second circuit being coupled to a carry-out terminal of the logic block; at least one logic block carry-in terminal; and means for using a signal on the logic block carry-in terminal or on one of the logic block carry-in terminals as a carry-in signal on the carry-in terminal of the first circuit.
Claim 15
Dependent Claim
43 words
A logic device as claimed in claim 14 wherein the second circuit comprises means for comparing a signal on the carry-out terminal of the first circuit with the carry-in signal on the first circuit, the means being useful for detecting an overflow condition.
Claim 16
Dependent Claim
82 words
A logic device as claimed in claim 15 wherein the means for comparing comprises: a first multiplexer for selecting between the carry-in signal of the first circuit and a first input signal to the second circuit; a second multiplexer for selecting between the carry-out signal of the first circuit and a second input signal to the second circuit; means for controlling the first and second multiplexers; and means for generating the XOR function of signals provided by the first and second multiplexers.
Claim 17
Dependent Claim
27 words
A logic device as claimed in claim 16 wherein the means for generating the XOR function of signals provided by the multiplexers comprises a combinatorial function generator.
Claim 18
Dependent Claim
32 words
A logic device as claimed in claim 1 comprising a logical function generator with at least two inputs, wherein each of the input terminals is a separate input to the function generator.
Claim 19
Dependent Claim
59 words
A logic device as claimed in claim 1 comprising: means for receiving a first input signal and placing the first input signal on said first input terminal; means for receiving a second input signal; means for selecting between placing the second input signal, the complement of the second input signal, and a constant value on the second input terminal.
Claim 20
Dependent Claim
54 words
A logic device as claimed in claim 19 wherein the means for selecting comprises: means for replacing the second input signal with a first constant value; means for controlling whether the second input signal will be replaced with the first constant value; and means for selecting whether the first constant value will be inverted.
Claim 21
Dependent Claim
58 words
A logic device as claimed in any preceding claim wherein each logic block has a carry-in terminal and a carry-out terminal, and the carry-out terminal of each logic block is coupled to at least one carry-in terminal of a logic block preceding the logic block and to the carry-in terminal of a logic block following the logic block.
Claim 22
Dependent Claim
55 words
A logic device as claimed in claim 21 wherein the logic blocks are positioned in a rectangular array of horizontal rows and vertical columns and wherein the logic block preceding each logic block and the logic block following it are positioned in the same column or in the same row as said each logic block.
Claim 23
Dependent Claim
31 words
A logic device as claimed in claim 21 or 22 wherein the logic block preceding each logic block and the logic block following it are contiguous to said each logic block.
Claim 24
Dependent Claim
102 words
A logic device comprising an array of configurable logic blocks, each logic block comprising: at least one stage, the or each stage comprising: at least a first input terminal and a second input terminal; a carry-in terminal; a carry-out terminal; dedicated circuitry for performing carry logic with at least three inputs and at least one output; wherein the three inputs or three of the at least three inputs comprise: a signal on the first input terminal; a signal on the second input terminal; and a signal on the carry-in terminal; and wherein the output is a carry function of the three inputs.
Claim 25
Dependent Claim
52 words
A logic device as claimed in claim 1 or 24 comprising: controllable means for selectively allowing the signal on the carry-in terminal to propagate to the carry-out terminal; or allowing the signal on the or one of the first input terminals and the second input terminal to propagate to said carry-out terminal.
Claim 26
Dependent Claim
22 words
A logic device as claimed in claim 1 or 24 comprising controllable means for providing a stored signal to the carry-out terminal.
Claim 27
Dependent Claim
34 words
A logic device as claimed in claim 1 or 24 comprising a third input terminal, and controllable means for selectively causing a signal on the third input terminal to propagate to the carry-out terminal.
Claim 28
Dependent Claim
36 words
A logic device as claimed in claim 24 comprising controllable means for selectively allowing the signal on the carry-in terminal to propagate to the carry-out terminal independently of signals on the first and second input terminals.
Claim 29
Dependent Claim
55 words
A logic device as claimed in claim 24 comprising second means for computing the carry function of the signal on the first input terminal, the signal on the carry-in terminal, and a complement of the signal on the second input terminal, and means for selecting between using the first means and using said second means.
Claim 30
Dependent Claim
23 words
An integrated circuit structure comprising an array of configurable logic blocks, the configurable logic blocks including dedicated hardware for performing a carry function.
Claim 31
Dependent Claim
40 words
A circuit structure as claimed in claim 30 comprising dedicated interconnect lines for interconnecting the hardware for performing the carry function in a first logic block to hardware for performing the carry function in at least a second logic block.
Claim 32
Dependent Claim
43 words
A circuit structure as claimed in claim 31 wherein the dedicated interconnect lines comprise lines for interconnecting the hardware for performing the carry function in a first logic block to hardware for performing the carry function in at least a third logic block.
Claim 33
Dependent Claim
93 words
A circuit structure as claimed in claim 32 comprising programmable interconnect lines, wherein the hardware for performing the carry function comprises: a carry-in terminal; a carry-out terminal; means for generating a carry-out signal in response to a carry-in signal on the carry-in terminal and input signals on selected ones of the programmable interconnect lines, and for placing the carry-out signal on the carry-out terminal; and means for selecting the carry-in signal of the third logic block from among at least carry-out signals on the carry-out terminals of the first and second logic blocks.
Claim 34
Dependent Claim
40 words
A circuit structure as claimed in claim 32 or 33 wherein the logic blocks are located in rows and columns within the integrated circuit structure, and the third logic block is positioned contiguous to the first and second logic blocks.
Claim 35
Dependent Claim
37 words
A circuit structure as claimed in claim 34 wherein the first logic block is positioned to the left of the third logic block and the second logic block is positioned above or below the third logic block.
Claim 36
Dependent Claim
32 words
A circuit structure as claimed in claim 34 wherein the first logic block is positioned above the third logic block and the second logic block is positioned below the third logic block.
Claim 37
Dependent Claim
41 words
A circuit structure as claimed in claim 32 or 33 wherein the logic blocks are positioned in rows and columns and the first and second logic blocks are located in the same row or same column as the third logic block.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.