Three input arithmetic logic unit with barrel rotator and mask generator
US5961635A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 30, 1993 |
| Grant date | Oct 5, 1999 |
| Priority date | — |
| Expiry date | Nov 30, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F7/575
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A three input arithmetic logic unit (230) that generates a combination of the three inputs that is selected by a function signal. The second input signal comes from a controllable barrel rotator (235). The rotate amount is a default rotate amount stored in a special data register, a predetermined set of bits of data recalled from a data register or zero. A one's constant source (236) is connected to the barrel rotator (235) to supply a multibit digital signal of "1". This permits generating a second input signal of the form 2.sup.N, with N being the rotate amount. The output of the barrel rotator (235) may be stored independently of the arithmetic logic unit (230) result. The third input signal comes from a multiplexer (233) that selects between an instruction specified immediate field, data recalled from a data register or a mask input from a mask generator (239). One preferred form of the mask has a number of right justified 1's corresponding to a mask input signal. This mask input signal may be the default barrel rotate amount or a predetermined number of the least significant bits of a third input signal as selected by a multiplexer. A second preferred form of the mask is selec…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.