摘要:
According to the invention, a structure is provided for driving a bus line that is both fast and small. Instead of a plurality of tristate buffers, one for each input signal, a plurality of multiplexers or gates is connected into a tree structure. The tristate enable line of the tristate buffer becomes the control line for enabling the tree structure to place its own input signal onto the bus instead of propagating the signal already on the bus. A buffer element then allows the resulting signal to be tapped from the bus. One embodiment of the invention includes lookahead logic similar to a lookahead carry chain. This allows large numbers of input lines to be connected to a bus line while retaining high speed. The symmetrical delay of a tree structure minimizes the greatest delay and thus increases predicted speed.
摘要:
The invention provides an FPGA comprising an array of identical tiles. Each tile comprises a logic block that includes a Configurable Logic Element (CLE). In one embodiment, the CLE is implemented in two similar portions called "slices". Each slice has a separate carry chain. In a CLE with four function generators, each carry chain incorporates the outputs of two function generators.
摘要:
The invention provides an FPGA interconnect structure preferably included in an array of identical tiles. Each tile comprises a logic block that includes a Configurable Logic Element (CLE) and an output multiplexer. Fast feedback paths are provided within the logic block to connect the CLE outputs to the CLE inputs, either directly or through an input multiplexer. The fast feedback paths bypass the output multiplexer and therefore provide faster feedback than can be obtained in most conventional FPGA logic blocks. In one embodiment, the fast feedback paths provide the ability for all function generators in one CLE to drive each other through fast feedback paths, regardless of how logic is mapped into the function generators of the CLE.
摘要:
The invention provides a Configurable Logic Element (CLE) preferably included in each of an array of identical tiles. A CLE according to the invention has four function generators. The outputs of two function generators are combined with a fifth independent input in a five-input-function multiplexer or function generator to produce an output that can be any function of five inputs, or some functions of up to nine inputs. The outputs of the other two function generators are similarly combined. The outputs of the two five-input-function multiplexers or function generators are then combined with a sixth independent input in a first six-input-function multiplexer or function generator, and with a different sixth independent input in a second six-input-function multiplexer or function generator. The two six-input-function multiplexers or function generators therefore produce two outputs of which one can be any function of six inputs; the other output can be any function of six inputs provided that five inputs are shared between the two 6-input functions. Some functions of up to nineteen inputs can also be generated in a single CLE.
摘要:
The invention allows the implementation of common wide logic functions using only two function generators of a field programmable gate array. One embodiment of the invention provides a structure for implementing a wide AND-gate in an FPGA configurable logic element (CLE) or portion thereof that includes no more than two function generators. First and second function generators are configured as AND-gates, the output signals (first and second AND signals) being combined in a 2-to-1 multiplexer controlled by the first AND signal, “0” selecting the first AND signal and “1” selecting the second AND signal. Therefore, a wide AND-gate is provided having a number of input signals equal to the total number of input signals for the two function generators. In another embodiment, a wide OR-gate is provided by configuring the function generators as OR-gates and controlling the multiplexer using the second OR signal.
摘要:
The invention provides a Configurable Logic Element (CLE) preferably included in each of an array of identical tiles. A CLE according to the invention has four function generators. The outputs of two function generators are combined with a fifth independent input in a five-input-function multiplexer or function generator to produce an output that can be any function of five inputs, or some functions of up to nine inputs. The outputs of the other two function generators are similarly combined. The outputs of the two five-input-function multiplexers or function generators are then combined with a sixth independent input in a six-input-function multiplexer or function generator. The six-input-function multiplexer or function generator therefore produces an output that can be any function of up to six inputs. Some functions of up to nineteen inputs can also be generated in a single CLE.
摘要:
The invention allows the implementation of common wide logic functions using only two function generators of a field programmable gate array. One embodiment of the invention provides a structure for implementing a wide AND-gate in an FPGA configurable logic element (CLE) or portion thereof that includes no more than two function generators. First and second function generators are configured as AND-gates, the output signals (first and second AND signals) being combined in a 2-to-1 multiplexer controlled by the first AND signal, “0” selecting the first AND signal and “1” selecting the second AND signal. Therefore, a wide AND-gate is provided having a number of input signals equal to the total number of input signals for the two function generators. In another embodiment, a wide OR-gate is provided by configuring the function generators as OR-gates and controlling the multiplexer using the second OR signal.
摘要:
The invention provides a Configurable Logic Element (CLE) preferably included in each of an array of identical tiles. A CLE according to the invention has four function generators. The outputs of two function generators are combined with a fifth independent input in a five-input-function multiplexer or function generator to produce an output that can be any function of five inputs, or some functions of up to nine inputs. The outputs of the other two function generators are similarly combined. The outputs of the two five-input-function multiplexers or function generators are then combined with a sixth independent input in a six-input-function multiplexer or function generator. The six-input-function multiplexer or function generator therefore produces an output that can be any function of up to six inputs. Some functions of up to nineteen inputs can also be generated in a single CLE.
摘要:
A multiplexer chain is coupled to two logic gates which in turn propagate their respective output signals in different directions, thereby providing bidirectional signal distribution. The output lines of multiple multiplexer chains are combined together using a logic gate chain to create a bus line with a larger number of drivers while substantially maintaining switching speed and flexibility in routability. In one embodiment, two OR chains propagate signals in opposite directions. The top OR chain combines the outputs of all the multiplexer chains to its left. Similarly, the bottom OR chain combines the outputs of all the multiplexer chains to its right. The output of the entire bus is provided at both the leftmost and the rightmost end of the OR chain. The bus output is also provided at tap points by combining the outputs of the top logic gate chain and the bottom logic gate chain using a logic gate. The top logic gate chain provides the outputs of all drivers to the left of the tap point while the bottom logic gate chain provides the outputs of all drivers to the right of the tap point.
摘要:
A programmable bidirectional interconnect circuit selectively provides either a buffered connection, a non-buffered connection, or a disconnection (tristate mode). The circuit includes six transistors coupled to a buffer and two signal lines.