8-6
IM 704420-01E
What Is an Interface Message
Interface messages are also referred to as interface
commands or bus commands. They are commands
that are issued by the controller. They are classified
as follows.
Uni-line messages
A single control line is used to transmit uni-line
messages. The following three messages are
available:
IFC (Interface Clear)
,
REN (Remote Enable)
,
and
IDY (Identify)
Multi-line messages
Eight data lines are used to transmit multi-line
messages. The messages are classified as follows:
• Address commands
These commands are valid when the instrument
is designated as a listener or as a talker. The
following five commands are available:
• Commands that are valid on an instrument
that is designated as a listener
GTL (Go To Local)
,
SDC (Selected Device
Clear)
,
PPC (Parallel Poll Configure)
,
and
GET (Group Execute Trigger)
• Commands that are valid on an instrument
that is designated as a talker
TCT (Take Control)
• Universal commands
These commands are valid on all instruments
regardless of the listener and talker designations.
The following five commands are available:
LLO (Local Lockout)
,
DCL (Device Clear)
,
PPU (Parallel Poll Unconfigure)
,
SPE
(Serial Poll Enable)
, and
SPD (Serial Poll
Disable)
• In addition, listener address, talker address, and
secondary commands are also considered
interface messages.
• The differences between
SDC
and
DCL
Of the multi-line messages,
SDC
messages are
those that require talker or listener designation
and
DCL
messages are those that do not require
the designation. Therefore,
SDC
messages are
directed at a particular instrument while
DCL
messages are directed at all instruments on the
bus.
Responses to Interface Messages
Responses to a uni-line message
•
IFC
Clears the talker and listener functions. Stops
output if data are being output.
•
REN
Switches between the remote and local modes.
•
IDY
Not supported.
Responses to a multi-line message (address
command)
•
GTL
Switches to the local mode.
•
SDC
Clears the program message (command) being
received and the output queue (see page 8-40).
•
GET
Same operation as the “
*TRG
” command.
• The
COMMunicate:WAIT
command is immediately
terminated.
•
PPC
and
TCT
: Not supported.
Responses to a multi-line message (universal
command)
•
LLO
Disables the LOCAL key on the front panel to
prohibit switching to the local mode.
•
DCL
Same operation as the SDC message.
•
SPE
Sets the talker function on all devices on the bus
to serial polling mode. The controller polls the
devices in order.
•
SPD
Clears the serial polling mode of the talker
function on all devices on the bus.
•
PPU
Not supported.
8.5
Responses to Interface Messages
