Optimizing and operating a time multiplexed programmable logic device

• US 5,761,483 A
• Filed: 08/18/1995
• Issued: 06/02/1998
• Est. Priority Date: 08/18/1995
• Status: Expired due to Term

• Current Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Original Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Inventors: Trimberger, Stephen M.
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): WALKER, TYRONE V
• Application Number:
  US08/516,588
• Time in Patent Office: 1,019 Days
• Field of Search: 395/500, 364/488, 364/489, 364/490, 364/491, 326/38, 326/39, 326/40, 326/41
• US Class Current: 716/117
• CPC Class Codes: G06F 30/34 for reconfigurable circuits, e.g. field programmable gate arrays [FPGA] or programmable logic devices [PLD]
• CPC Class Codes: H03K 19/17704 the logic functions being realised by the interconnection of rows and columns
• CPC Class Codes: H03K 19/17758 for speeding up configuration or reconfiguration
• CPC Class Codes: H03K 19/1776 for memories

Abstract

A method of optimizing a time multiplexed programmable logic device (PLD) includes entering a circuit design for the PLD, mapping the design to the physical resources of the PLD (wherein the physical resources include configurable logic elements), determining an appropriate micro cycle for each configurable logic element in the design, placing the resources on the PLD, and connecting the resources. Optimizing the design may include reducing the number of look up tables or reducing the logic depth of the look up tables. If the configurable logic elements include sequential logic elements, then the optimizing step includes rescheduling the sequential logic elements. A method of operating a time multiplexed PLD in a logic engine mode includes programming the PLD to implement a design in stages, wherein each stage is one configuration, sequencing the PLD through all the configurations, and storing the results of the logic performed in one configuration in a plurality of micro registers for use in subsequent configurations. In one embodiment, the PLD includes a plurality of combinational elements and sequential logic elements, wherein the values stored by the sequential logic elements are stored in the micro registers.

Claims

1. A computer-implemented method of designing a time multiplexed programmable logic device, comprising:

entering a circuit design for said programmable logic device;

mapping said circuit design to the physical resources of said programmable logic device, wherein said physical resources include configurable logic elements;

determining an appropriate micro cycle for each configurable logic element in said design;

placing said resources on said programmable logic device; and

connecting said resources.

2. The computer-implemented method of claim 1 further comprising optimizing said design.

3. The computer-implemented method of claim 2 wherein said optimizing includes reducing the number of said configurable logic elements to implement said design.

4. The computer-implemented method of claim 2 wherein said optimizing includes reducing the logic depth of said configurable logic elements to implement said design.

5. The computer-implemented method of claim 2 wherein said circuit design includes sequential logic elements and said optimizing includes rescheduling said sequential logic elements.

6. A computer-implemented method of designing a time multiplexed programmable logic device, comprising:

entering a circuit design for said programmable logic device;

mapping said design to the physical resources of said programmable logic device, wherein said physical resources include configurable logic elements;

simultaneously determining an appropriate micro cycle for each configurable logic element in said design and placing said resources on said programmable logic device; and

connecting said resources.

7. A method of time multiplexing a programmable logic device comprising:

scheduling the logic of said programmable logic device to be evaluated in a plurality of micro cycles; and

scheduling the logic of a critical path in said programmable logic device to be evaluated in sequential micro cycles.

8. A computer-implemented method of operating a time multiplexed programmable logic device in a logic engine mode, comprising:

programming said programmable logic device to implement a design in stages, wherein each stage is one configuration;

sequencing said programmable logic device through at least one of the configurations;

storing the results of the logic performed in one configuration in a plurality of micro registers for use in subsequent configurations.

9. The computer-implemented method of claim 8 wherein said programmable logic device includes a plurality of combinational elements and sequential logic elements, wherein the values stored by said sequential logic elements are stored in said micro registers.

10. The computer-implemented method of claim 8 further including isolating the bits associated with an active configuration during an operation on the bits of at least one inactive configuration.

11. The computer-implemented method of claim 10 wherein said bits of at least one inactive configuration are user data bits.

12. The computer-implemented method of claim 11 further including a plurality of memory slices on said programmable logic device, wherein the bits associated with said active configuration are provided in at least two slices.