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5.1.2 Interrupt Service Table (IST)
When the CPU begins processing an interrupt, it references the interrupt
service table (IST). The IST is a table of fetch packets that contain code for
servicing the interrupts. The IST consists of 16 consecutive fetch packets.
Each interrupt service fetch packet (ISFP) contains eight instructions. A simple
interrupt service routine may fit in an individual fetch packet.
The addresses and contents of the IST are shown in Figure 5−1. Because
each fetch packet contains eight 32-bit instruction words (or 32 bytes), each
address in the table is incremented by 32 bytes (20h) from the one adjacent
Figure 5−1. Interrupt Service Table