Interrupt Controller (8259A)
All 256 interrupt types are located in absolute memory locations 0
through 3FFh, which make up the V20’s interrupt vector table (see
Figure 12-1). Each type in the interrupt vector table requires 4 bytes
of memory and stores a code segment address and an instruction
pointer address. Locations 0 through 3FFh should be reserved for the
interrupt vector table alone.
Furthermore, memory locations 00
through 7Fh (types 0-31) are reserved for use by Intel Corporation for
Intel hardware and software products. To maintain compatibility with
present and future Intel products, do not use these locations.
INTERRUPT TYPE 255
INTERRUPT TYPE 254
INTERRUPT TYPE 2
INTERRUPT TYPE 1
INTERRUPT TYPE 0
.
.
.
3FFh
3FCh
3FBh
3F8h
Bh
8h
7h
4h
3h
0h
Figure 12–1. V20 Interrupt Vector Table.
12-5
