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Data processor control unit having an interrupt service using instruction prefetch redirection

  • US 4,709,324 A
  • Filed: 11/27/1985
  • Issued: 11/24/1987
  • Est. Priority Date: 11/27/1985
  • Status: Expired due to Term
First Claim
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1. In a data processing system having a data processor for executing intructions and a control unit for providing said instructions to the data processor, said control unit selectively providing prefetched normal instructions in an absence of an interrupt request from a peripheral device and providing prefetched interrupt instructions in response to an interrupt request, a method for minimizing instruction cycles in which no instructions are being executed by the data processor associated with interrupting instruction flow to execute an interrupt service routine in response to an interrupt request, comprising the steps of:

  • detecting receipt of a request from the peripheral device to interrupt normal instruction flow from the control unit to the data processor;

    providing a control signal for a duration of at least one instruction cycle in response to the request to interrupt normal instruction flow;

    redirecting normal instruction prefetches for the at least one instruction cycle in response to the control signal to provide at least one interrupt instruction prefetch, said at least one interrupt instruction prefetch being initiated before said prefetched normal instructions complete execution;

    redirecting said at least one interrupt instruction prefetch immediately after the at least one instruction cycle duration of the control signal to continue providing normal instruction prefetches, said normal instruction prefetches being initiated before said at least one prefetched interrupt instruction completes execution.

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