Keithley 194 Instruction Manual page 272

APPENDIX G
Unaddress Commands
The two unaddress commands are used by the controller
to remove any talkers or listeners from the bus. ATN is true
when these commands are asserted.
UNL (Unlisten)-Listeners are placed in the listener idle
state by UNL.
UNT (Untalk)-Any previously commanded talkers will
be placed in the talker idle state by UNT.
Device-Dependent Commands
The purpose of device-dependent commands will depend
on instrument configuration. Generally, these commands
are sent as one or more ASCII characters that command
the device to perform a specific action For example, the
command string I<OX is used to control the measurement
range of the Model 194.
The IEEE-488 bus treats thcsc commands as data in that
ATN is false when the commands xc transmitted
Command Codes
Command codes for the various commands that use the
data lines are summarized in Figure G-3. I iexadecimal and
and decimal values for the various commands are listed
in Table G-2.
G-5