DMAF2
Controller
Board
Jumpers
~The
DMAF2
contains
a
number
of
jumper
programmable
options
as
described
below.
HALT/BUS
REQ
When
in
the
HALT
mode,
DMA
transfers
will
take
place
by
halting
the
processor.
When
in
the
BUS.
REQ
position,
transfers
will
be
made
by
utilizing
the
bus
request
feature
of
the
6809.
This
jumper
should
normally
be
in
the
HALT
position.
PRE
COMP/NORM.
When
in
the
PRE COMP
position
the
DMAF2
controller
boardwill
automatically
pre-compensate
(shift)
certain
bits
written
to
disk
by
250
nS
on
inner
tracks
while
in
the
double
density
mode.
Most
disk
drives
require
write
pre-compensation
and
this
jumper
should
be
left
in
the
PRE
COMP
position.
BA/BA
&
BS”
When. in
the
BA
position
the
controller
will
respond
to
the
processor's
DMA
acknowledge
by
looking
at
only
the
BA
(bus
available)
line.
For
6809
systems
with
the
DMAF2
jumper
in
the
BA-&
BS
position,
the
controller
will
respond
only
when
BA
and
BS
are
high.
Normally
a
jumper
on
the
6809
processor
board
automatically
puts
the
BA
& BS status
on
the
BA
line
so
the
DMAF2
jumper
should
be
left
in
the
BA
position.
1
MHz/2MHz.
.
This
jumper
selects
the
MEMORY
READY
line
timing
in
6809
systems.
The
jumper
should
be
in
the
1 MHz
position
for
1
MHz
computer
systems
and
in
the
2 MHz
position
for
systems
operating
a
:
Ze
.
’
.
MR/NORM
When
in
the
MR
position
the
system's
slow
memory
line
will
be
pulled
low
each
time
an
access
is
made
to
the
DMAF2 board.
This
jumper
should
be
in
the
MR
position
for
all
6809
systems
running
at
2
MHz.or
when
using
certain
dynamic
memory
boards.
32K/56K
a
:
This.
jumper
changes
the
decoding
so
that
the
DMAF2:
will
respond
to
different
addresses.
It
should
be
in
the
32K
.
position
for
6800
operation
and
the
56K
position
for
6809
systems.
_
UPPER/LOWER
This
jumper
selects
which
512
byte
block
that
the
DMAF2 will
respond
to
of
the
1K
block
selected
by
the
0
-
7°
jumper.
This
jumper
should
normally
be
in
the
LOWER
position.
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13
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