Gtl (Go To Local); Dcl (Device Clear); Sdc (Selective Device Clear); Get (Group Execute Trigger) - Keithley 2002 User Manual

3.5.4 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 16"
SLEEP 3
PRINT #1, "local 16"

3.5.5 DCL (device clear)

The DCL command may be used to clear the IEEE GPIB
interface 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 2002 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"

3.5.6 SDC (selective device clear)

The SDC command is an addressed command that performs
essentially the same function as the DCL command. How-
ever, since each device must be individually addressed, the
SDC command provides a method to clear only selected
instruments instead of clearing all instruments simulta-
neously, as is the case with DCL.
Program fragment
PRINT #1, "clear 16"

3.5.7 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 2002 will re-
act to this trigger if it is the programmed control source. GET
can also be used as the pre-trigger for the reading buffer. The
control source is programmed from the SCPI :TRIGger sub-
system.
With the instrument programmed and waiting for a GPIB
trigger, the following program fragment will provide the
GET.
' Place 2002 in remote
' Wait 3 seconds
' Take 2002 out of remote
' Clear all devices
' Clear 2002
Program fragment
PRINT #1, "trigger 16"
This sends IEEE-488 commands UNT UNL LISTEN 16
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.)

3.5.8 SPE, SPD (serial polling)

The serial polling sequence is used to obtain the Model 2002
serial poll byte. The serial poll byte contains important infor-
mation about internal functions, as described in paragraph
3.7.6. Generally, the serial polling sequence is used by the
controller to determine which of several instruments has
requested service with the SRQ line. However, the serial
polling sequence may be performed at any time to obtain the
status byte from the Model 2002.
Program fragment
PRINT #1, "spoll 16"
INPUT #2, S
PRINT S
3.6 Front panel aspects of IEEE-488
operation
The following paragraphs discuss aspects of the front panel
that are part of IEEE-488 operation, including messages, sta-
tus indicators, and the LOCAL key.
3.6.1 Error and status messages
Table 2-4 summarizes the error and status messages associ-
ated with IEEE-488 programming. Note that the instrument
may be programmed to generate an SRQ, and command que-
ries can be performed to check for specific error conditions.

3.6.2 IEEE-488 status indicators

The REM (remote), TALK (talk), LSTN (listen), and SRQ
(service request) annunciators show the present IEEE-488
status of the instrument. Each of these indicators is briefly
described below.
REM — This indicator shows when the instrument is in the
remote state. Note that REM does not necessarily indicate
the state of the REN line, as the instrument must be
addressed to listen with REN true before the REM indicator
IEEE-488 Reference
' Trigger 2002 from over
the bus
' Serial poll the 2002
' Read the serial poll byte
' Display the decimal value of
the serial poll byte
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