Add-on programs with code verification and control
US4321667A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 31, 1979 |
| Grant date | Mar 23, 1982 |
| Priority date | — |
| Expiry date | Oct 31, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C29/40
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Expandable memory system having add-on modules beginning at fixed address boundaries, e.g., 2K (K=1024), and having verification and authorization features. A non-volatile memory stores a bit corresponding to each 2K memory boundary. When an add-on program is authorized at a particular boundary address, the corresponding bit is set. The base program checks each bit and, if it is set, reads the first location of the corresponding add-on program. If the data read from the new module matches some reference, e.g., the boundary address itself, then program control branches to the add-on program. Additional verification features include cyclic redundancy checks of the added code. Alternative operation includes branching to a verified add-on program that tests its own authorization bit which, if reset, causes a branch to the next verified add-on program, and so on.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.