Intel Comprehensive Guide to the iAPX 432 Interface Processor Architecture

iAPX 432 Interface Processor Architecture Reference Manual

The fault port is serviced by a 432 fault handling process where one of four actions may be taken:

oCorrect the reason for the fault and OOmplete any partially perfonmed function by completing the unfinished steps.

oCorrect the reason for the fault, rewind any partially performed function steps, and then retry the function.

oDecide to reflect the process-level fault to the context-level.

o "Crash" the system.

The first two actions represent the method that an operating system can use to extend the 432 architecture. For example, an operating system's virtual InP.1IDry implementation considers a "storage not associated" fault as a nonmal occurrance and retrieves the missing menory segment. With the segment available, the fault handler can decide to simulate the canpletion of the function or unwind the partially completed function and rerun it.

Processor-Level Faults

Processor-level faults, the most severe level of faults, occur when an IP detects a condition which jeopardizes further operation by the processor. Bus errors and alarms are examples of such occurrences. In response to the first processor-level fault encountered, the IP reports the fault in the fault information area of the processor data segment, updates the processor status to "faulted", and signals

an interrupt to inform the attached processor. If a second processor...;level fault occurs before the AP has recorded the fault information, the IP closes all five of its windows into 432 memory, including the control window, signals that a fatal error has occurred and indicates that the Peripheral Subsystem should be reset (see FATAL/ and PSR pin descriptions in the iAPX 43203 Interface Processor Data Sheet, Order Number 171874).

WINOOW-MAPPED DA':m TRANSFER

Information about faults which occur during data transfer through the windows is recorded in the mapping facility fault infonmation area oontained in the IP processor object. This information is accessible to the AP through the control window. Each window (0 through 4) has a separate fault information area. When the fault occurs, the IP deposits the fault infonmation, closes the window, tuts the window in the error state, and interrupts the Attached Processor. Only open windows can generate window mapping faults.

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