Front-Panel Gpib Operation - Keithley 2651A Reference Manual

Section 2: General operation
DCL (device clear)
Use the device clear command (DCL) to clear the 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 2651A receives a DCL command, it clears the Input Buffer and Output Queue,
cancels deferred commands, and clears any command that prevents the processing of any other
device command. A DCL does not affect instrument settings and stored data.
SDC
The selective device clear command (SDC) is an addressed command that performs essentially the
same function as the DCL command. However, since each device must be individually addressed,
the SDC command provides a method to clear only selected instruments instead of clearing all
instruments simultaneously, as is the case with DCL.
GET
The group execute trigger command (GET) is a GPIB trigger that is used to trigger the instrument to
take readings from a remote interface.
SPE, SPD
Use the serial polling sequence to obtain the Model 2651A serial poll byte. The serial poll byte
contains important information about internal functions (see
the serial polling sequence is used by the controller to determine which of several instruments has
requested service with the SRQ line. The serial polling sequence may be performed at any time to
obtain the status byte from the Model 2651A.

Front-panel GPIB operation

This section describes aspects of the front panel that are part of GPIB operation, including messages,
status indicators, and the LOCAL key.
Error and status messages
See Error summary list
488 programming. The instrument can be programmed to generate an SRQ, and command queries
can be performed to check for specific error conditions.
GPIB status indicators
The remote (REM), talk (TALK), listen (LSTN), and service request (SRQ) indicators show the GPIB
bus status. Each of these indicators is described below.
REM
This indicator shows when the instrument is in the remote state. When the instrument is in remote, all
front panel keys, except for the EXIT (LOCAL) key and OUTPUT ON/OFF control, are locked out.
When REM is turned off, the instrument is in the local state, and front panel operation is restored.
2-80
Model 2651A High Power System SourceMeter® Instrument Reference Manual
(on page 8-2) for a list of status and error messages associated with IEEE-
Status Model (on page E-1)). Generally,
2651A-901-01 Rev. A / March 2011