FPGA logic element with variable-length shift register capability
US6388466B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 27, 2001 |
| Grant date | May 14, 2002 |
| Priority date | — |
| Expiry date | Apr 27, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K19/1737
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A logic element for a programmable logic device (PLD) can be configured as a shift register of variable length. An array of memory cells in the logic element is divided into two or more portions. The memory cells of each portion supply values to a corresponding output multiplexing circuit, thereby enabling the logic element to function as a lookup table by combining the outputs of the multiplexing circuits. However, each portion is also configurable as a shift register. The portions can function as separate shift registers, or can be concatenated to function as a single shift register. In some embodiments, the portions can also be concatenated with shift registers in other logic elements. Because two or more output multiplexing circuits are available, two or more taps are provided, one from each portion of the memory array.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.