Method and apparatus for controlling reselection of a bus by overriding a prioritization protocol
US5414818A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 6, 1990 |
| Grant date | May 9, 1995 |
| Priority date | — |
| Expiry date | Apr 6, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F13/36
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The present invention provides a method and apparatus for dynamically modifying the priority of access to a bus, where the bus has control and arbitration functions distributed among the devices coupled to the bus, with each device having a fixed priority level. Access to the bus by particular devices is selectively inhibited, preventing them from asserting their fixed priority level. In a preferred embodiment, the present invention provides control over the reselection of a SCSI bus by a plurality of SCSI devices coupled to the bus by providing a pseudo busy signal to SCSI devices from which reselection is not desired. In this fashion, an initiator may issue a plurality of commands to the SCSI devices and control the order in which the devices will be serviced when ready. A plurality of pseudo busy circuits are provided, with one coupled to each device on the bus. Each pseudo busy circuit is controlled by a control signal from the initiator. The pseudo busy circuit intercepts the busy line of the SCSI bus and provides a pseudo busy signal to the busy line input of the device when instructed by the initiator; although this requires additional control lines in conjunction with the S…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.