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Programmable Interrupt Vectors in Processors

IP.com Disclosure Number: IPCOM000050438D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Hennet, PP: AUTHOR [+4]

Abstract

Described is a method to select under program control the vector number of an interrupt of a processor that uses a vectored interrupt scheme. Using this method, the new state of the processor after an interrupt can be selected dynamically, even from outside the processor.

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Programmable Interrupt Vectors in Processors

Described is a method to select under program control the vector number of an interrupt of a processor that uses a vectored interrupt scheme. Using this method, the new state of the processor after an interrupt can be selected dynamically, even from outside the processor.

Many processor architectures use a vectored interrupt scheme to determine the processor state after an interrupt. For each possible interrupt type, there is one interrupt vector in main storage. An interrupt vector contains the state that the processor adopts after a corresponding interrupt. This state usually consists of status information and the address in memory from Which the processor will fetch instructions after the interrupt.

An interrupt from an interrupt source outside the processor, such as an I/O device, triggers the following sequence of events (see the figure). The interrupt is signaled to the processor on the interrupt request line. The processor then issues a vector number request signal. The interrupt source recognizes the request and puts the vector number on the vector number input bus, from where the processor reads it. This vector number determines from which interrupt vector in the main memory of the processor the new processor state is loaded. The processor memory bus and the vector number input bus may use the same physical bus. In existing architectures using vectored interrupts, each interrupt source has a fixed interrupt vector number assigned. This vector number is determined by the wired connection between the interrupt source and the vector num...