Three input arithmetic logic unit forming mixed arithmetic and boolean combinations
US5596763A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 30, 1993 |
| Grant date | Jan 21, 1997 |
| Priority date | — |
| Expiry date | Nov 30, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2207/382
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A three input arithmetic logic unit (230) forms a mixed arithmetic and Boolean combination of three multibit input signals. The arithmetic logic unit (230) first forms a Boolean combination and then forms an arithmetic combination. The current instruction drives an instruction decoder (250, 245) that generates the functions signals F0-F7 which control the combination formed. The three input arithmetic logic unit (230) preferably employs a set of bit circuits (400), each forming carry propagate, generate and kill signals. These signals may employed with a multilevel logic tree circuit and a carry input to produce a bit resultant and a carry output to the next bit circuit. This structure permits formation of selected arithmetic, Boolean or mixed arithmetic and Boolean function of the three input signals based upon the current instruction. Selection of the function signals enables the combination to be insensitive to one of the input signals, thus performs a two input function of remaining input signals. The instruction itself may include the function signals and function modification bits, or the function signals and function modification signals may be stored in a special data regis…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.