Keithley 237

SECTION3
IEEE-488
Reference
3.5.1
REN (Remote
Enable)
The remote enable command is sent to the Model
236/237/238
by
the controller to set
up
the instrument
for remote operation. Generally, the instrument should
be placed
in
the remote mode before
you
attempt to pro-
gram it over the bus. Simply setting REN
true
does not ac-
tually place the instrument
in
the remote state. Instead
the instrument
must
be addressed to listen after setting
REN true before
it
goes into remote.
Note that the instrument need not
be
in
remote to
be
a
talker.
Programming Example - This sequence is automati-
cally performed
by
the controller
when
the following is
typed
into the keyboard
..
REMOTE716
After the RETURN key is pressed, the instrument is in the
remote state, as indicated
by
the
RMT
light.
If
not, check
to see that the instrument is set to the proper primary ad-
dress 16,
and
check to see that the
bus
connections are
properly made.
Note that all front panel controls except for
LOCAL (and,
of course, POWER) are inoperative while the instrument
is in remote. You can restore normal front panel opera-
tion by pressing the
LOCAL
key.
3.5.2
IFC
(Interface
Clear)
The IFC command is sent
by
the controller to place the
Model236/237 /238
in
the local, talker
and
listener idle
states. The
unit
responds to the IFC command
by
cancell-
ing front panel TALK
or
LISTEN lights,
if
the instrument
was previously placed in one of those states.
To send the IFC command, the controller need only set
the IFC line true for a minimum
of
100J!Sec.
Programming
Example-
Before demonstrating the IFC
command,
turn
on
the TLK indicator
with
the following
+
At
this
point, the TLK light should
be
on. The IFC com-
mand
can
be
sent
by
entering the following statement
into the computer:
ABORTI07
After the RETURN key is pressed, the
TLK
indicator
turns off, indicating that the instrument has gone into the
talker idle state.
3.5.3
LLO (Local
Lockout)
The
LLO command is used to prevent local operation of
the instrument. After the
unit
receives
LLO, all its front
panel controls except POWER are inoperative.
Programming
Example-
The LLO
command is sent
by
entering the following statements:
REMOTE716
LOCAL LOCKOUT
7
After the second statement is executed, the instrument's
front panel controls are locked out, including the
LOCAL
key.
To restore front panel operation after asserting
LLO,
as in
the following example, enter:
LOCAL7
3.5.4
GTL (Go To Local)
and
Local
The GTL command
is
used
to take the instrument
out
of
the remote state. Operation of the front panel keys will
also
be
restored
by
GTL unless
LLO
is
in
effect. To cancel
LLO,
you
must
set REN false.
Programming
Example-
Place the instrument in
there-
mote state
with
the following statement:
REMOTE716
statement:
Now
send GTL
with
the following statement:
ENTER 716;A$
LOCAL
716
3-6
+