IEEE-488 Reference
3-6
3.6.3 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. In this state, press-
ing LOCAL will not restore control to the front panel. The
GTL command restores control to the front panel.
Program fragment
PRINT #1, "remote 27" ' Place 6517A in
remote
PRINT #1, "local lockout" ' Lock out front
panel (including
LOCAL key)
SLEEP 6 ' Wait 6 seconds
PRINT #1, "Local 27" ' Restore front
panel operation
3.6.4 GTL (go to 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.
Program fragment
PRINT #1, "remote 27" ' Place 6517A in
remote
SLEEP 3 ' Wait 3 seconds
PRINT #1, "local 27" ' Take 6517A out of
remote
3.6.5 DCL (device clear)
The DCL command may be used to clear the IEEE GPIB in-
terface and return it to a known state. Note that the DCL
command is not an addressed command, so all instruments
equipped to implement DCL will do so simultaneously.
When the Model 6517A receives a DCL command, it clears
the Input Buffer and Output Queue, cancels deferred com-
mands, and clears any command that prevents the processing
of any other device command. A DCL does not affect instru-
ment settings and stored data.
Program fragment
PRINT #1, "clear" ' Clear all devices
3.6.6 SDC (selective device clear)
The SDC command is an addressed command that performs
essentially the same function as the DCL command. Howev-
er, since each device must be individually addressed, the
SDC command provides a method to clear only selected in-
struments instead of clearing all instruments simultaneously,
as is the case with DCL.
Program fragment
PRINT #1, "clear 27" ' Clear 6517A
3.6.7 GET (group execute trigger)
GET is a GPIB trigger that is used as an arm, scan and/or
measure event to control operation. The Model 6517A will
react to this trigger if it is the programmed control source.
GET can also be used as the pre-trigger for the reading buff-
er. The control source is programmed from the SCPI :TRIG-
ger subsystem.
With the instrument programmed and waiting for a GPIB
trigger, the following program fragment will provide the
GET.
Program fragment
PRINT #1, "trigger 27" ' Trigger 6517A
from over the
bus
This sends IEEE-488 commands UNT UNL LISTEN 27
GET. When the command is executed, the trigger event oc-
curs. (The command TRIGGER just sends GET. Any other
listeners are triggered when the command is executed.)
3.6.8 SPE, SPD (serial polling)
The serial polling sequence is used to obtain the Model
6517A serial poll byte. The serial poll byte contains impor-
tant information about internal functions, as described in
paragraph 3.8.6. Generally, the serial polling sequence is
used by the controller to determine which of several instru-
ments has requested service with the SRQ line. However, the
serial polling sequence may be performed at any time to ob-
tain the status byte from the Model 6517A.
Program fragment
PRINT #1, "spoll 27" ' Serial poll the 6517A
INPUT #2, S ' Read the serial poll
byte
PRINT S ' Display the decimal
value of the serial
poll byte
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