Non-Processor Request and Grant: Difference between revisions
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A '''Non-Processor Request''' is one of the two kinds of bus requests on the [[UNIBUS]]; it is used exclusively to gain control of the UNIBUS's data section so that the device may perform a [[DMA]] cycle. | A '''Non-Processor Request''' is one of the two kinds of bus requests on the [[UNIBUS]] and [[QBUS]]; it is used exclusively to gain control of the UNIBUS's data section so that the device may perform a [[DMA]] cycle. | ||
The name comes from the fact that the device cannot request that the [[CPU]] perform any action (i.e. an [[interrupt]]) while the device has control of the bus. | The name comes from the fact that the device cannot request that the [[CPU]] perform any action (i.e. an [[interrupt]]) while the device has control of the bus. | ||
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[[Category: UNIBUS]] | |||
[[Category: QBUS]] | |||
Revision as of 23:36, 19 December 2018
A Non-Processor Request is one of the two kinds of bus requests on the UNIBUS and QBUS; it is used exclusively to gain control of the UNIBUS's data section so that the device may perform a DMA cycle.
The name comes from the fact that the device cannot request that the CPU perform any action (i.e. an interrupt) while the device has control of the bus.
A device gaining control of the UNIBUS via an NPR request may perform more than one master-slave cycle before relinquishing control of the bus, however.
