Specifications
AUTO-VECTOR
INTERRUPTS
Seven
level$
of
interrupts
are
available
on
the
68000,
in
increasins
level
of
priorit~.
The
hiShest
level
of
interrupt
is
non-
maskable.
The
auto-vectors
are
assisned
as
follows:
I
Level
I
Ad~re5s(hex)
I
VS100
Device
1-------1--------------1----------------------------------------
I 0 I
----------
I
No
Interrupt
1-------1--------------1----------------------------------------
I 1 I
64
I HOIJse
Cursor
1-------1--------------1----------------------------------------
I 2 1
68
1
Ke~board
Receive/Transmit
1-------1--------------1----------------------------------------
I 3 1 he I
Tablet
1-------1--------------1----------------------------------------
1 4 1
70
1
BBA
Command
Done
1-------1--------------1----------------------------------------
1 5 1
74
1
Link_Tran$ition
or
Link_Error
I-------I--------------I------------~---------------------------
1 6 I
78
I
Vertical
S'::Inc
l-------I--------------l----------------------------------------
I 7 I
7C
I
BBA
Non-Existent
UBW
Memor~
Access
1-------1--------------1----------------------------------------
Ke~board
and
Tablet
Interrupts
occur
under
two
conditions:
When
the
USART
HoldinS
Resister
receives
a
b~te
of
information
from
the
device,
a
receiver
interrupt
is
Senerated.
When
the
USART
HoldinS
ReSister
transmits
a
b~te
of
information
to
the
device,
a
transmitter
interrupt
is
Senerated.
Receiver
inter-
rupts
are
cleared
by
readinS
the
data
from
the
HoldinS
Resist~r.
Transmitter
interrupts
are
cleared
b~
disablinS
the
transmitter.
Vertical
S~nc
interrupts
occur
at
ever'::l
vertical
s~nc;
that
is,
every
1/60
second.
House
Buttons
are
polled
durinS
vertical
sync
handlinS,
for
the
purpose
of
reportins
loSin
events
to
the
host.
Vertical
S~nc
interrupts
are
cleared
b~
performins
a
read
operation
on
address
$8000E1.
Mouse
interrupts
occur
ever~
time
the
mouse
is
moved.
The
information
is
stored
and
used
durins
vertical
s~nc
handlins
to
update
the
mouse
cursor
when
it
is
attached.
House
interrupts
are
cleared
b~
readinS
data
from
the
mouse
cursor.
Link_Error
Interrupts
are
iSnored,
but
Link_Transition
Interrupts
are
used
to
determine
whether
or
not
to
turn
on
the
fibre's
LED
driver
at
the
VS100
end
of
the
s~stem.
We
store
the
information
of
the
current
state
in
memor~,
and
examine
Link_Available
to
determine
whether
to
turn
the
LED
on
or
off.
Link_Transition
occurs
when
the
state
of
the
LED
driver
at
the
UBW
end
of
the
s~stem
chanSes.
Each
interrupts
sets
a
flas
indicatins
that
it
occurred.
(e.S.,
levelS
sets
the
Ilink_transitionl
flaS).
These
flass
are
all
cleared
on
powerup.