Browse Prior Art Database

Method of Keeping Distributed Interrupt Requests Consistent

IP.com Disclosure Number: IPCOM000120317D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 83K

Publishing Venue

IBM

Related People

Hilgendorf, R: AUTHOR [+3]

Abstract

A hardware interrupt in a system may have many sources. Owing to I/O pin limitations on the hardware components, it may be preferable to have only one physical source for the interrupt to the processor.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method of Keeping Distributed Interrupt Requests Consistent

      A hardware interrupt in a system may have many sources.
Owing to I/O pin limitations on the hardware components, it may be
preferable to have only one physical source for the interrupt to the
processor.

      In the system described, all bus units (BUs) on the I/O
distribution bus 10 send their interrupt requests by command to the
bus adapter (BA) which, in turn, presents the physical interrupts to
the processor.  The BA maintains a set of pointers in a register 90
by which the processor is able to determine the source of the
interrupt.  A BU requesting an interrupt normally has several
possible sources for this request.  However, the pointer in the BA
has to be active as long and only as long as at least one source
in the BU is also active.  The problem arises when the interrupt
source in the BU is reset.  In this case, the corresponding bit in
pointer register 90 of the BA needs to be reset too.

      Below three possible solutions are described which all have
drawbacks.
           The pointer in the BA is reset by the processor prior to
resetting an interrupt source in the BU.
           -    If more than one interrupt source is active, the BA
has to set the pointer once more.
           The pointer in the BA is reset by the processor after all
interrupt sources in the BU have been reset.
           -    In the time between resetting the source and
resetting the pointer, a new interrupt may have come up which then
will not be detected.

      The pointer in the BA is reset by a command from the BU after
the pro...