Bus request line
From Computer History Wiki
Bus request lines are used in a number of bus architectures (for example, the UNIBUS and QBUS), for a device controller to communicate to the CPU (or whatever circuitry is controlling the bus) that it is requesting an interrupt or DMA bus cycle.
The device controller does this by asserting the bus request line to the CPU, to notify it. Such lines are usually instantiated as wired-OR lines, to enable them to be used in broadcast mode.
See also
- Non-Processor Request and Grant - UNIBUS DMA request and grant lines
- DMA Request and Grant - QBUS DMA request and grant lines
