Front-Panel Gpib Operation - Keithley 2657A Reference Manual

Model 2657A High Power System SourceMeter® Instrument Reference Manual Section 2: General operation
GET
The group execute trigger (GET) command is a GPIB trigger that triggers the instrument to take
readings from a remote interface.
SPE, SPD
Use the serial polling sequence to obtain the Model 2657A serial poll byte. The serial poll byte
contains important information about internal functions (see Status model (on page E-1)). Generally,
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 2657A.

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
The front-panel display may show error and status messages (see Displayed error and status
messages (on page 2-72)). See Error summary list (on page 8-3) for a list of status and error
messages that are associated with IEEE-488 programming.
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 is illuminated when the instrument is in the remote control state. When the instrument is
in the remote control state, all front-panel keys, except for the EXIT (LOCAL) key and OUTPUT
ON/OFF control, are locked out. When REM is off, the instrument is in the local control state and
front-panel operation is restored.
TALK
This indicator is on when the instrument is in the talker active state. Place the instrument in the talk
state by addressing it to talk with the correct talk command. TALK is off when the instrument is in the
talker idle state. Place the instrument in the talker idle state by sending a UNT (untalk) command,
addressing it to listen, or by sending the IFC (interface clear) command.
LSTN
This indicator is on when the Model 2657A is in the listener active state, which is activated by
addressing the instrument to listen with the correct listen command. LSTN is off when the instrument
is in the listener idle state. Place the instrument in the listener idle state by sending UNL (unlisten),
addressing it to talk, or by sending the IFC (interface clear) command over the bus.
SRQ
You can program the instrument to generate a service request (SRQ) when one or more errors or
conditions occur. When this indicator is on, a service request has been generated. This indicator
stays on until the serial poll byte is read or all the conditions that caused SRQ are cleared.
2657A-901-01 Rev. B/December 2012 2-87