FPGA interconnect structure with high-speed high fanout capability

• US 5,907,248 A
• Filed: 02/09/1998
• Issued: 05/25/1999
• Est. Priority Date: 02/26/1997
• Status: Expired due to Term

• Current Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Original Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Inventors: Young, Steven P., Bauer, Trevor J.
• Primary Examiner(s): Santamauro, Jon
• Assistant Examiner(s): ROSEEN, RICHARD R
• Application Number:
  US09/020,369
• Time in Patent Office: 470 Days
• Field of Search: 326/39, 326/41
• US Class Current: 326/39
• CPC Class Codes: H03K 19/1737 using multiplexers H03K19/1738 takes precedence
• CPC Class Codes: H03K 19/17704 the logic functions being realised by the interconnection of rows and columns
• CPC Class Codes: H03K 19/17796 for physical disposition of blocks

Abstract

The invention provides an FPGA interconnect structure preferably included in an array of identical tiles. A combination of single-length lines connecting to adjacent tiles and intermediate-length lines connecting to tiles several tiles away creates an interconnect hierarchy which allows any logic block to be connected to any other logic block, yet also allows for fast paths to both adjacent tiles and tiles some distance away. Longer interconnect lines may be included as a third level of hierarchy to permit interconnection of widely separated tiles. In a preferred embodiment, from a given tile an intermediate-length line connects to the tile three tiles away, then continues and connects to the tile six tiles away. In this embodiment, the intermediate-length line does not connect to the intervening tiles one, two, four, and five tiles away. According to a second aspect of the invention, high fanout signals can be distributed to any tile in the array. A signal on a horizontal long line traverses a row of tiles, in which it makes contact with the logic block in each tile through hex lines and single-length lines. The horizontal single-length lines connected to some horizontal hex lines can programmably drive vertical long lines. Using these programmable connections, the signal on the horizontal long line bus is transferred to the vertical long lines. From the vertical long lines, a high-fanout signal is delivered to an array of tiles.

Claims

1. An interconnect structure for distributing high-fanout signals to logic blocks in an FPGA, comprising:

an array of logic blocks arranged in rows and columns, said logic blocks each having inputs and at least one output;

a plurality of intermediate-length lines extending a length greater than two of said logic blocks;

a plurality of long lines extending a length greater than a length of said intermediate-length lines, a first plurality of said long lines extending in a first direction and a second plurality of said long lines extending in a direction perpendicular to said first direction; and

means for programmably interconnecting one of said first plurality of said long lines and one of said second plurality of said long lines through one of said plurality of intermediate-length lines, said interconnecting means comprising a first PIP connecting said one of said first plurality of said long lines to said one of said plurality of intermediate-length lines.

2. The interconnect structure of claim 1, wherein said intermediate-length lines are hex lines.

3. The interconnect structure of claim 1, wherein said intermediate-length lines extend in said first direction.

4. The interconnect structure of claim 1, further comprising:

a plurality of single-length lines, each such single-length line being of sufficient length to connect to said inputs and outputs of two such adjacent logic blocks; and

wherein;

said means for programmably interconnecting one of said first plurality of said long lines and one of said second plurality of said long lines through one of said plurality of intermediate-length lines comprises at least one of said plurality of single-length lines.

5. The interconnect structure of claim 4, wherein said intermediate-length lines are hex lines.

6. The interconnect structure of claim 4, wherein said intermediate-length lines and said single-length lines extend in said first direction.

7. The interconnect structure of claim 4, wherein said interconnecting means further comprises:

a second PIP connecting said one of said plurality of intermediate-length lines to said one of said plurality of single-length lines; and

a third PIP connecting said one of said plurality of single-length lines to said one of said second plurality of long lines.

8. The interconnect structure of claim 7, wherein said third PIP is located within one of said logic blocks.

9. An interconnect structure for distributing high-fanout signals in an FPGA, comprising:

a column of tiles, each such tile comprising a logic block having at least one input;

a plurality of intermediate-length lines extending through at least a portion of said column of tiles, each such intermediate-length line being at least three such tiles long, each such intermediate-length line connecting a first such tile to at least second and third such tiles at least two and three tiles away;

at least one long line extending through at least a portion of said column of tiles, said long line having a length greater than a length of said intermediate-length lines; and

means for programmably interconnecting said one long line to at least one such input in each said logic block, said interconnecting means comprising;

at least one such intermediate-length line; and

a PIP connecting said long line to said intermediate-length line.

10. The interconnect structure of claim 9, wherein said means for interconnecting said long line to at least one such input in each said logic block comprises at least two programmable interconnection points (PIPs), such that:

a first PIP programmably connects said long line to said intermediate-length line;

a second PIP programmably connects said intermediate-length line to said each said logic block input; and

the number of PIPs programmably connecting said long line to each such logic block input is the same.

11. The interconnect structure of claim 9, further comprising:

a plurality of single-length lines, each such single-length line being of sufficient length to connect to said inputs and outputs of two such adjacent logic blocks; and

wherein;

said interconnecting means further comprises one such single-length line.

12. An interconnect structure for distributing high-fanout signals in an FPGA, comprising:

a column of at least N tiles, each such tile comprising a logic block having at least one input;

a plurality of intermediate-length lines extending through at least N/2 of said tiles;

at least one long line extending through at least N of said tiles; and

means for programmably interconnecting said one long line to at least one such input in at least N such logic blocks, said interconnecting means comprising;

at least one such intermediate-length line; and

a PIP connecting said long line to said intermediate-length line.

13. The interconnect structure of claim 12, wherein N is 12.

14. The interconnect structure of claim 12, wherein:

said at least one long line is connectable to one such intermediate-length line every N/2 tiles; and

said at least one long line is unconnectable to any of said plurality of intermediate-length lines in all other of said tiles.

15. An interconnect structure for distributing high-fanout signals in an FPGA, comprising:

a column of tiles, each such tile comprising a logic block having at least one input;

a plurality of intermediate-length lines extending through at least a portion of said column of tiles, each such intermediate-length line being at least three such tiles long, each such intermediate-length line connecting a first such tile to at least second and third such tiles at least two and three tiles away;

at least one long line extending through at least a portion of said column of tiles, said long line having a length greater than a length of said intermediate-length lines; and

means for programmably interconnecting said one long line to at least one such input in each said logic block, said interconnecting means comprising;

at least one such intermediate-length line; and

a PIP connecting said long line to said intermediate-length line.

16. An interconnect structure for distributing high-fanout signals in an FPGA, comprising:

a column of at least N tiles, each such tile comprising a logic block having at least one input, said column therefore comprising a column of N logic blocks;

a plurality of intermediate-length lines extending through at least N/2 of said tiles;

at least one long line extending through at least said N tiles; and

means for programmably interconnecting said one long line to at least one such input in each of said N logic blocks, said interconnecting means comprising;

at least one such intermediate-length line; and

a PIP connecting said long line to said intermediate-length line.

17. The interconnect structure of claim 16, wherein N is 12.

18. The interconnect structure of claim 16, wherein:

said at least one long line is connectable to one such intermediate-length line every N/2 tiles; and

said at least one long line is unconnectable to any of said plurality of intermediate-length lines in all other of said tiles.