Applications—
7A42
Figure
3-11. Two ECL level waveforms, A without bias offset, B with a -2 volt bias offset.
7A42
PROBE
OFFSET
FEATURE
The
7A42
features
a
built-in digital
voltmeter
which
was
designed
to
accommodate
the
P6230
Variable Bias/Offset
Probe.
Pressing
the
7A42's
PROBE
OFFSET
pushbutton
while
in
the program
channel mode
with
the
SWITCHING
THRESHOLD
VOLTS
monitor
turned on,
will
cause
the
button to
light
red. This
red
light
indicates
that
the
digital
voltmeter
is
enabled
and
ready
to
measure
the
probe
offset.
Place
the
tip
of
the
probe
into
the
7A42
’
s
PROBE
TIP
jack
and
set
the
probe
offset
to
the
desired
voltage.
While
holding the
probe
tip
in
the
jack,
push
the
PROBE
OFFSET
button
again
until
it
lights
green. The offset forthat
particular
channel
has now been
measured,
acquired,
and
will
be compensated
for
automatically
when
setting
the
threshold
for
that
channel.
In
other
words,
the
user,
having
acquired
the
probe
offset
for a
particular
channel,
need
not
take
that offset
into
account
when
setting
the
logic threshold
for
that
channel.
When
using
the
P6230,
remember
the
first
step
is
to
acquire
the
probe
offset
value
into
the
7A42. Next
set
the
Switching
Threshold Voltage
with
the
LEVEL buttons
to
a
value
appropriate
for
the
logic
family
under
test. The
Switching
Threshold
Voltage
at
the
probe
tip
is
indicated
in
the
numerical
display.
REV
JUL
1984
3-16