Microprocessor interrupt processing

TL;DR: In this article, an integrated circuit data processor receives interrupt level signals from external circuitry which represent a priority level associated with the external circuitry, and these signals are compared with signals representing the current operating level of the processor, and an interrupt pending output is generated if the priority level is higher than the operating level.

Abstract: An integrated circuit data processor receives interrupt level signals from external circuitry which represent a priority level associated with the external circuitry. These signals are compared with signals representing the current operating level of the processor, and an interrupt pending output is generated if (1) the priority level is higher than the operating level; or (2) a maximum priority level is received. Upon the occurrence of the interrupt pending output, the current instruction program is interrupted, and an instruction program associated with the external circuitry is executed. The processor transmits a signal back to the external circuitry indicating that the interrupt request has been granted and receives a vector number from the external circuitry. A first acknowledgment signal from the external circuitry causes the vector number to be latched in the processor. A second acknowledgment signal from the external circuitry causes a vector to be internally generated. Error circuitry is provided to detect spurious interrupts.