Table of Contents
Advertisement
Operation
4.9.4
Stand-alone
and
master/slave
One
method
to
expand
system
size
is
to
connect
up
to five
mainframes
in
a
master/slave configuration,
where
all
units
are
daisy-chained
for
serial
communication and
control.
Sys-
tem
operations
are
performed through
the
master
unit,
either
over
the
IEEE-488
bus or
the
master's front
panel (including
the
light
pen).
A
master/slave
system appears
as a single unit
(and
IEEE-488
address) with a
maximum
size
of
8
rows by
360
columns.
Selection
of
stand-alone or master/slave oper-
ation
is
done
with
a
menu
item.
This
action
is
performed
by
pressing
the
MENU
key of
the
desired
master
mainframe
until
the display reads
STAND
ALONE.
Next,
scroll
up
or
down
to
the
MASTER
message.
Then,
press
the
ENTER
key
to
initiate
die
master/slave
loop.
If
the
loop
is
complete
(MASTER/SLAVE
OUT
to
MAS-
TER/SLAVE
IN
in
a daisy chain
among
all
units),
the
master
unit will exit
menu mode
and
the other
units will
display
SLAVE
1,
SLAVE
2, etc.
(The
slave
number
is
determined
by
the
unit's
position
in
the loop.)
If
the
loop of
DIN
cables
is
not closed, the
master
will
display
the
message
M/S
ERROR
and
all
units will
remain
as stand-alones.
As
previously described
in
paragraph
3.5,
the
MASTER/
SLAVE
OUT
and
MASTER/SLAVE
IN
rear
panel
connec-
tors
are
used
to
connect
DIN
cables
in
a closed loop.
The
connector pinouts
are
defined
in
Figure 4-12.
7
8^
)
O
5
7
'
1
^
11
When
the units are
powered up one
at
a
time, they
will
display
the
message
M/S
LOOP
DOWN
until
all
units are
powered.
CAUTION
When
it
is
necessary
to cycle
power on
a
slave
unit,
turn
off
all
units in the
master/slave configuration.
This
pro-
cedure prevents
the
open communi-
cation
and
control loop
from
putting the
slave unit in
an
undesirable
state.
During
master/slave operation,
most
front
and
rear
panel
controls
of
the slave units are
inactive.
Table 4-6
shows
which
controls
and
indicators
remain
active for slave
units.
Pin
Master/S
lave IN
Master/Slave
Out
1
M/S TRIGGER
(fow
true)
2
ALLREADY
3
LPRESET
(low
true)
4
LPSENSE
(tow
true)
5
RxDATA
6-8
Chassis
Ground
M/S
TRIGGER
(low
true)
ALLREADY
LPRESET
(low
true)
LPSENSE
(low
true)
TxDATA
Chassis
Ground
Figure 4-12
Master/slave connectors
After interconnecting
and powering up
all
units,
one
unit
is
selected
to
be
a master.
The
master
unit
communicates
with
the slaves
only
when
necessary;
it
does
not
continuously monitor
the
status
of
the
closed-loop
configuration.
Hence,
a
di.sconnected master/
slave
loop cable
is
not
detected,
and
the
message
M/S
ERROR
is
not displayed,
until
the
master
attempts
to
send or
receive data
around
the loop.
The
steps
taken
by
a master
unit
to
recover
from
an
M/S
ERROR
are outlined
below;
1
.
The
master
stops
processing
IEEE-488
bus
commands,
returns
to
stand-alone operation,
and
disables.
2.
The
slave units
remain
the
same
as
before
the error
occurred.
3.
To
re-initialize
the loop,
ensure
that
master/slave cables
are secure,
and
select
master/siave operations
from
the
mainframe
that
previously
was
master.
4-16
Advertisement
Table of Contents
