IBM 5150 Hardware Reference Manual

Vectors With Special Meanings
Interrupt 1 BH - Keyboard Break Address
This vector points to the code to be exercised when the CTRL
BREAK keys are depressed on the keyboard. The vector is
r-"\ invoked while responding to the keyboard interrupt, and control
should be returned via an
lRET instruction. The power on routines
initialize this vector to point to an
lRET instruction, so that nothing
happens when
CTRL BREAK keys are depressed unless
the application program sets a different value.
Control may be retained by this routine, with the following
problems. The BREAK may have occurred during interrupt
processing, so that one
or mor End of Interrupt commands must
be set to the 8259 controller. Also, all
I/O devices should be reset in
case an operation was underway at that time.
Interrupt 1 CH - Timer Tick
This vector points to the code to be executed on every tick of the
system clock. This vector
is invoked while responding to the
timer interrupt, and control should be returned via an
lRET
~ instruction. The power on routines initialize this vector to point
. to an
lRET instruction, so that nothing happens unless the
application modifies the pointer.
It is the responsibility of the
application to save and restore all registers that will be modified.
Interrupt IDH - Video Parameters
This vector points to a data region containing the parameters
required for the initialization of the 6845 on the video card. Note
that there are four separate tables, and all four must be
reproduced if all modes
of operation are to be supported. The
power on routines initialize this vector to point to the para-
meters contained in the ROM video routine.
Interrupt 1 EH - Diskette Parameters
This vector points to a data region containing the parameters
required for the diskette drive. The power on routines initialize
the vector to point to the parameters contained in the
ROM
diskette routine. These default parameters represent the
specified values for any IBM drives attached to the machine.
Changing this parameter block to reflect the specifications
of
the other drives attached may be necessary.
3-5

IBM 5150 Specifications

General

Brand	IBM
Model	5150
Category	Desktop
Language	English