Keithley 263 Instruction Manual page 206

Table F-l. IEEE-488 Bus Command Summary
Command Type
Uniline
Universal
Addressed
Unaddressed
Device-dependeni
Command
REN (Remote Enable)
EOI ' EOI '
IFC (Interface Clear) IFC (Interface Clear)
ATN (Attention) ATN (Attention)
SRQ SRQ
Multiline Multiline
LLQ (Local Lockout) LLQ (Local Lockout)
DCL (Device Clear)'
SPE (Serial Enable)
SPD Serial Poll Disable)
SDC (selective Device Clear
GTL (Go To Local)
UNL (Unlisten)
UNT (Untalk)
*X = Don't Care.
REN (Remote Enable)-REN is sent to set up instruments
on the bus for remote ooeration. When REN is true.
devices will be removed f&n the local mode. Depending
on device configuration, all front panel controls except the
LOCAL button (if the device is do equiped) may be lock-
ed out when REN is true. Generally, REN should be sent
before attempting to program inshuments over the bus.
EOI (End Or Identify)-EOI is used to positively identify
the last byte in a multi-byte transfer sequence, thus allow-
ing data words of various lengths to be transmitted easily.
IFC fInterface 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 com-
mand is transmitted. As with all multiline commands,
these commands are transmitted with ATN true.
X0 (local Lockout)-LLQ is sent to the instrument to lock
<.:llt their front panel controls.
F-4
ATN Line
X
X
X
L.ow
X
Low
Low
Low
Low
LOW
Low
Low
Low
High
Sets up devices for remote operation.
Locks out local operation.
Returns device to default conditions.
Enables serial polling.
Disables serial polling.
Returns unit to default conditions.
Returns device to local.
Removes all listeners from bus.
Removes any talkers from bus.
Programs Model 595 for various modes.
DCL (Device Clear)-DCL is used to return instruments
to some default state. Usually, instruments return to their
power-up conditions.
SPE (Serial Poll Enable)-SPE is the first step in the serial
polling sequence, 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 poll@
sequence.
Addressed Multiline Commands
Addressed commands are multiline commands that must
be preceded by the device listen address before that in-
strument will respond to the command in question. Note
that only the addressed device will res ond to these com-
mands. Both the command and the a i dress preceding it
are sent with ATN true.
SDC (Selective Device Clea+The SDC command per-
forms essentially the same function as the DCL command
except that only the addressed device responds. General-
ly, instruments 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 in-
struments, GTL also unlocks front panel controls if they
were previously locked out with the LLO command.