Three input arithmetic logic unit with shifter and mask generator
US5974539A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 30, 1993 |
| Grant date | Oct 26, 1999 |
| Priority date | — |
| Expiry date | Nov 30, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F5/015
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A three input arithmetic logic unit (230) generates a combination of the three inputs that is selected by a function signal. The second input signal comes from a controllable shifter (235). The shift amount is a default shift 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 shifter (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 shift amount. The output of the shift (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 shift amount or a predetermined number of the least significant bits of the third input signal as selected by a multiplexer. A second preferred form of the mask is selected one of the left most 1, the right…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.