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Operation
4.9.1
Digital
I/O
The
ITL-compatible
DIGITAL
I/O
port
has eight data
lines
for inputs,
eight
data
lines for
outputs,
and two
control
lines
for
handshaking.
The
pinout
for the rear
panel
DB-25
con-
nector
is
shown
in
Figure
4-8. Status
of
the
input
lines
is
viewed and
states
of
the
output
lines
are
programmed
through
the
first
menu
item.
With no
input
connections
and
power-up
default conditions
for the output, the
alphanumeric
display
will
read the following decimal
values:
IN
255
OUT
000
The
digital
inputs are logic
high with
no
connections.
Use
the control
line
INLATCH
(low
true) to latch
in
the
digital
inputs
when
changing an
input
state.
To
program
the
digital
output
states,
select the
desired deci-
mal
value with
the
data entry
keys and
press
ENTER.
You
can
now
key
in
another value
and
press
ENTER,
or press
CANCEL
to exit
menu
mode,
or press
MENU
to
continue
to
the
next
item.
Each
time
the
digital
outputs
are
programmed,
even
if
the
states
are
not
changed,
the control
line
OUT-
PULSE
is
brought
low.
Figure 4-8
Digital
I/O
port
With
master/slave configurations,
only
the
DIGITAL
I/O
port
of
the
master
unit
is
available
for
viewing and
programming.
4.9.2
External trigger
If
triggers
are enabled,
and
external
trigger
is
selected as
a
source, a
TTL-compatible
pulse
of
at least
bOOnsec
duration
at
the rear
panel
EXTERNAL TRIGGER
INPUT
jack
trig-
gers
the
Model
707
A.
The
input
BNC
jack
is
shown
in
Figure
4-9.
EXTERNAL
TRIGGER
INPUT
MATRIX
READY
OUTPUT
Figure
4-9
Rear
panel
BNC
jacks
The
unit
can be
programmed
with a
menu
item
for
which
edge
(falling
or
rising)
of
the
external
trigger
pulse causes a
transfer
of stored setup data
to
the
relays.
Sample
trigger
pulses are
shown
in
Figure
4-10.
To
select
which
pulse
edge
triggers,
use the
MENU
key
to
choose
the
menu
item
for
external
trigger.
The
power-up
default display
will
read:
EXT
TRIG
FALL
4-14
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