Motorola MVME2300 Series manual Architectural Notes, Raven Interrupt Controller

Models: MVME2300 Series

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Raven Interrupt Controller

Architectural Notes

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The hardware and software overhead required to update the Task Priority register synchronously with instruction execution may far outweigh the anticipated benefits of the Task Priority register. To minimize this overhead, the interrupt controller architecture should allow the Task Priority register to be updated asynchronously with respect to instruction execution. Lower-priority interrupts may continue to occur for an indeterminate number of cycles after the processor has updated the Task Priority register. If this is not acceptable, the interrupt controller architecture should recommend that if the Task Priority register is not implemented with the processor, the Task Priority register should be updated only when the processor enter or exits an idle state.

Only when the Task Priority register is integrated within the processor, (such that it can be accessed as quickly as the MSRee bit defined in the Programming Notes section, for example), should the architecture require the Task Priority register to be updated synchronously with instruction execution.

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Page 161
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Motorola MVME2300 Series manual Architectural Notes, Raven Interrupt Controller