System
Interrupts
The 80286 microprocessor provides a non-maskable interrupt
(NMI) bit
that
can
be set and reset
with
system programs. An
interrupt controller provides another
19-1evels
of
system interrupt.
The Intel
8259A
interrupt controller chip U107
is
the master chip.
Cascaded
to
the master chip are
two
other 8259A chips.
Each
chip
has
an
8-bit interrupt request function. The primary function
of
the third controller chip
is
keyboard and input device interface.
The following chart gives the port addresses
of
the interrupt
controllers.
020H Master
8259A
Port 0
021H
Master
8259A
Port 1
OAOH
Slave
8259A
(#2) Port 0
OA1H
Slave
8259A
(#2) Port 1
07CH
Slave
8259A
(#3) Port 0
07DH
Slave
8259A
(#3) Port 1
Interrupt Controller
The following figure indicates
the
possible interrupt vector offset
mappings. The current address
in
hex
is
given
in
the parentheses.
In
the far right hand column
is
the function
of
the interrupt vector
employed by
HP
Vectra.
20
Processor Board
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