High performance product term based carry chain scheme
US6201409A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 8, 2000 |
| Grant date | Mar 13, 2001 |
| Priority date | — |
| Expiry date | Feb 8, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F7/506
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A macrocell for a programmable logic device includes a carry generator for generating a carry input to the macrocell, the carry generator having an inverting input and at least one non-inverting input. A carry decoupler controls the carry generator and allows any macrocell to be decoupled from a next adjacent macrocell. An XOR gate having a first input is coupled to the output of the carry generator and a second input thereof is connected to a logic input to the macrocell. A register is coupled to the output of the XOR gate. A macrocell output selector includes a first input coupled to an output of the register and a second input coupled to the output of the XOR gate. A method for implementing a carry chain for macrocells within a product term based programmable logic device according to the present invention includes the steps of logically ANDing a carry input with a user-configurable input to produce an intermediate result; selecting one of two carry input product terms from a product term array based upon the intermediate result, the selected carry product term being a carry input to a current macrocell; propagating the carry input of the current macrocell to a next macrocell; a…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.