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command
write
IOW,
This
command
line
instructs an
the data
bus.
may be driven
on
It
controller. This signal
DMA
read
command
MEMR,
memory
This
command
instructs
line
the data
onto
bus.
may be driven
It
controller. This signal
DMA
command
write
MEMW,
memory
This
command
line
instructs
the
data
present
bus.
on
It
orthe
controller. This signal
DMA
requests
DRQ1-DRO3,
DMA
These
asynchronous channel requests used
lines
are
for
peripheral devices
to gain
by
with
DRQ3 being
prioritized
the
is
generated
highest.
A
request
an active level (high).
to
A
the corresponding
until
DACK line
DACK 0-3,
DMA
acknowledge
These
lines
are
DACK 0
and
requests
(DRQ1-DRQ3)
They
are
memory
(DACK 0).
address
enable
AEN,
This
used
degate the processor and other
line is
to
vices
the
channel
from
l/O
place.
When this
active high,
line is
had control
over the address bus, the data bus, the read
command
and
lines (memory
lines (memory
and
l/O).
28
read the data
device
l/O
to
the processor
the
for
by
is
active
low.
the
data
drive
to
its
memory
the processor
the
or
by
active
is
low.
the
store the data
to
memory
may be driven
the
by
processor
active
is
low.
to
9
1
services.
DMA
are
They
the
lowest and
DRQ1
being
a
DRQ
line
bringing
by
DRQ
line
must be held high
active.
goes
to
0
3
used
-3
to
acknowledge
DMA
refresh system
to
dynamic
active
low.
de—
transfers
take
to allow
DMA
to
the
controller
DMA
the
command
and
write
I/O)
terminal count
T/C,
This
line
a
pulse when
provides
channel
DMA
reached.
IS
O
CARD SLCTD,
card selected
line is
activated
This
the system
Signals
board that
and that appropriate
be
directed
either
to
read
J10. Connectors J3
through
but
the system board should
pm,
collector device.
The
voltages are available
following
board
channel:
l/O
-
+5V DC
plus or minus 5%
pins.
{N
DC
plus or minus 10%
°
pin.
.
DC
plus or minus 5%
+_12V
pin.
-
DC
plus or minus 10% located on
-12V
pin.
GND
-
(ground) located on
O
the
terminal count for any
This signal
is
active
high.
cards
in
expansion
slot
by
the card
had
been selected
drivers on
the system board should
from
or
to write
to
expansion
J10 are
tied
together
be driven
by
an
the system
on
located
two
on
connector
located
on
one connector
located
on
one connector
one connector
three connector
pins.
J8.
lt
slot
at this
open
29
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