Bus Commands - Keithley 2500 User Manual

Models 2500 and 2502 User's Manual

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 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 D-1
IEEE-488 bus command summary
Command
type
Uniline
Multiline
Universal
Addressed
Unaddressed
Common
SCPI
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Command
REN (Remote Enable)
EOI (End Or Identify)
IFC (Interface Clear)
ATN (Attention)
SRQ (Service Request)
LLO (Local Lockout)
DCL (Device Clear)
SPE (Serial Poll Enable)
SPD (Serial Poll Disable)
SDC (Selective Device
Clear)
GTL (Go To Local)
UNL (Unlisten)
UNT (Untalk)
–
–
IEEE-488 Bus Overview
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 instru-
ments for particular operations.
D-7
Table D-1.