Direct input/output in a virtual memory system
US4777589A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 28, 1985 |
| Grant date | Oct 11, 1988 |
| Priority date | — |
| Expiry date | Jun 28, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2212/206
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A virtual memory system is used to control access to I/O device address space in accordance with a preferred embodiment of the present invention. In a virtual memory system, access to pages within a processor's address space are assigned to each application program. Each I/O device is assigned two pages of address space. One page is considered to be privileged, and the other unprivileged. Each I/O device register is associated with an address in each of the two pages of its I/O device address space. Address space is global. What is meant by global is that physical memory locations map to the same virtual memory space regardless of what process is running on the processor. Access codes accompanied by a write disable bit are used to control process access to various addresses.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.