13-6
IM 765501-01E
13.5 Responses to Interface Messages
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 types 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 types 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 types are available.
LLO (Local Lockout), DCL (Device Clear), PPU
(Parallel Poll Unconfigure), SPE (Serial Poll
Enable), and SPD (Serial Poll Disable)
Other Interface Messages
Listener address, talker address, and secondary
commands are also considered interface messages.
The Differences between SDC and DCL
In 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 section
16.3.5).
• The COMMunicate:WAIT command is
immediately terminated.
• GET
Same operation as the *TRG command.
• PPC and TCT
Not supported.
Responses to a Multi-Line Message (Universal
Command)
• LLO
Disables LOCAL 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.