Bus Commands - Keithley 6517B Reference Manual

Appendix D: IEEE-488 bus overview

Bus commands

The instrument may be given a number of special bus commands through the IEEE-488 interface.
This section briefly describes the purpose of the bus commands, which are grouped into the following
four categories:
1. Uniline commands: Sent by setting the associated bus lines true. For example, to assert REN
(remote enable), the REN line would be set low (true).
2. Multiline commands: General bus commands that are sent over the data lines with the ATN line
true (low).
3. Common commands: Commands that are common to all devices on the bus; sent with ATN high
(false).
4. SCPI commands: Commands that are particular to each device on the bus; sent with ATN (false).
These bus commands and their general purposes are summarized in the following table.
IEEE-488 bus command summary
Command type
Uniline
Multiline
Universal
Addressed
Unaddressed
Common
SCPI
D-6
Command
REN (remote enable)
EOI
IFC (interface clear)
ATN (Attention)
SRQ
LLO (local lockout)
DCL (device clear)
SPE (serial enable)
SPD (serial poll disable)
SDC (selective device clear)
GTL (go to local)
UNL (unlisten)
UNT (untalk)
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Model 6517B Electrometer Reference Manual
State of
ATN line Comments
X Set up devices for remote operation
X Marks end of transmission
X Clears interface
Low Defines data bus contents
X Controlled by external device
Low Locks out local operation
Low Returns device to default conditions
Low Enables serial polling
Low Disables serial polling
Low Returns unit to default conditions
Low Returns device to local
Low Removes all listeners from the bus
Low Removes any talkers from the bus
High Programs IEEE-488.2 compatible
instruments for common operations
High
Programs SCPI compatible instruments
for specific operations
6517B-901-01 Rev. C / August 2015