Keithley 2182, User Manual, Page: 186 / 339

11-12 Remote Operation
SPE, SPD (serial polling)
Use the serial polling sequence to obtain the Model 2182 serial poll byte. The serial poll byte
contains important information about internal functions. 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 2182.
Program Fragment
WaitSRQ:
CALL SPOLL (7, poll%, status%)
‘ Serial poll the 2182.
IF (poll% AND 64) = 0 THEN GOTO WaitSRQ ‘ Loop back if no SRQ.
Front panel GPIB operation
The following paragraphs describe aspects of the front panel that are part of GPIB operation,
including messages, status indicators, and the LOCAL key.
Error and status messages
See Appendix B for a list of error and status messages associated with IEEE-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 REM (remote), TALK (talk), LSTN (listen), and SRQ (service request) annunciators
show the GPIB bus status. Each of these indicators is described below.
• REM – This indicator shows when the instrument is in the remote state. REM does not
necessarily indicate the state of the REM line, as the instrument must be addressed to
listen with REM true before the REM indicator turns on. When the instrument is in
remote, all front panel keys, except for the LOCAL key, are locked out. When REM is
turned off, the instrument is in the local state, and front panel operation is restored.
• TALK – This indicator is on when the instrument is in the talker active state. Place the
unit in the talk state by addressing it to talk with the correct MTA (My Talk Address)
command. TALK is off when the unit is in the talker idle state. Place the unit in the talker
idle state by sending an UNT (Untalk) command, addressing it to listen, or sending the
IFC (Interface Clear) command.
• LSTN – This indicator is on when the Model 2182 is in the listener active state, which
is activated by addressing the instrument to listen with the correct MLA (My Listen
Address) command. LSTN is off when the unit is in the listener idle state. Place the unit
in the listener idle state by sending UNL (Unlisten), addressing it to talk, or 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 have ceased to exist.