IEEE-488 Bus Overview
C-4
by the controller or other devices depending on the direction
of data transfer. The following is a description of each com-
mand. Each command is sent by setting the corresponding
bus line true.
• REN (Remote Enable) — REN is sent to set up instru-
ments on the bus for remote operation. When REN is
true, devices will be removed from the local mode.
Depending on device configuration, all front panel con-
trols except the LOCAL button (if the device is so
equipped) may be locked out when REN is true. Gener-
ally, REN should be sent before attempting to program
instruments over the bus.
• EOI (End or Identify) — EOI is used to positively iden-
tify the last byte in a multi-byte transfer sequence, thus
allowing data words of various lengths to be transmitted
easily.
• IFC (Interface Clear) — IFC is used to clear the inter-
face 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.
Table C-1
IEEE-488 bus command summary
Command
type
Command
State of
ATN
line
Comments
Uniline
Multiline
Universal
Addressed
Unaddressed
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
Set up devices for remote operation.
Marks end of transmission.
Clears interface.
Defines data bus contents.
Controlled by external device.
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 the bus.
Removes any talkers from the bus.
C.4
Bus commands
The instrument may be given a number of special bus com-
mands through the IEEE-488 interface. The following para-
graphs briefly describe the purpose of the bus commands that
are grouped into the following categories.
• 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).
• Multiline commands — General bus commands that are
sent over the data lines with the ATN line true (low).
• Common commands — Commands that are common to
all devices on the bus and are sent with ATN high
(false).
• SCPI commands — Commands that are particular to
each device on the bus and are sent with ATN (false).
These bus commands and their general purpose are summa-
rized in Table C-1.
C.4.1 Uniline commands
ATN, IFC, and REN are asserted only by the controller. SRQ
is asserted by an external device. EOI may be asserted either
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
Summary of Contents for 708A
Page 135: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 136: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 137: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 138: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 139: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 145: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 146: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 147: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 148: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 149: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...
Page 150: ...Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com ...