Bus commands
The instrument may be given a number of special bus commands through the IEEE-488 in-
terface. This section briefly describes the purpose of the bus commands which are grouped into
the following three categories.
1. Uniline Commands — Sent by setting the associated bus lines true. For example, to as-
sert REN (Remote Enable), the REN line would be set low (true).
2. Multiline Commands — General bus commands which 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 purpose are summarized in Table E-1.
Table E-1
IEEE-488 bus command summary
Command
type
Command
State of
ATN
line
Comments
Uniline
Multiline
Universal
Addressed
Unaddressed
Common
SCPI
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)
—
—
X
X
X
Low
X
Low
Low
Low
Low
Low
Low
Low
Low
High
High
Set up devices for remote operation.
Marks end of transmission.
Clears interface.
Defines data bus contents.
Controlled by external device.
Locks our 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 the bus.
Removes any talkers from the bus.
Programs IEEE-488.2 compatible
instruments for common operations.
Programs SCPI compatible instru-
ments for particular operations.
E-8 IEEE-488 Bus Overview
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