Keithley 6430, Instruction Manual

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D-8 IEEE-488 Bus Overview
IFC (Interface Clear)
— IFC is used to clear the interface and return all devices to the
talker and listener idle states.
ATN (Attention) — The controller sends ATN while transmitting addresses or multiline
commands.
SRQ (Service Request)
— SRQ is asserted by a device when it requires service from a
controller.
Universal multiline commands
Universal commands are those multiline commands that require no addressing. All devices
equipped to implement such commands will do so simultaneously when the commands are
transmitted. As with all multiline commands, these commands are transmitted with ATN true.
LLO (Local Lockout) — LLO is sent to the instrument to lock out the LOCAL key and thus
all the front panel controls.
DCL (Device Clear)
— DCL is used to return instruments to some default state. Usually,
instruments return to the power-up conditions.
SPE (Serial Poll Enable) — SPE is the fi rst step in the serial polling sequences, which is
used to determine which device has requested service.
SPD (Serial Poll Disable)
— SPD is used by the controller to remove all devices on the bus
from the serial poll mode and is generally the last command in the serial polling sequence.
Addressed multiline commands
Addressed commands are multiline commands that must be preceded by the device listen
address before that instrument will respond to the command in question. Note that only the
addressed device will respond to these commands. Both the commands and the address preced-
ing it are sent with ATN true.
SDC (Selective Device Clear)
— The SDC command performs essentially the same func-
tion as the DCL command except that only the addressed device responds. Generally, instru-
ments return to their power-up default conditions when responding to the SDC command.
GTL (Go To Local)
— The GTL command is used to remove instruments from the remote
mode. With some instruments, GTL also unlocks front panel controls if they were previously
locked out with the LLO command.
GET (Group Execute Trigger) — The GET command is used to trigger devices to perform
a speci fi c action that depends on device con fi guration (for example, take a reading). Although
GET is an addressed command, many devices respond to GET without addressing.