11-8
IM 2558A-01EN
11.4 Responses to Interface Messages
Multi-line Messages
Eight data lines are used to transmit multi-line messages. The messages are classified as follows:
• Address Commands
Some address commands are valid when a device is designated as a listener, and some are
valid when it is designated as a talker. The following five commands are available.
Commands available to a device designated as a listener
• GTL (Go To Local)
• SDC (Selected Device Clear)
• PPC (Parallel Poll Configure)
• GET (Group Execute Trigger)
Commands available to a device designated as a talker
• TCT (Take Control)
• Universal commands
Universal commands are available to all devices regardless of their listener or talker designation.
The following five commands are available.
• LLO (Local Lockout)
• DCL (Device Clear)
• PPU (Parallel Poll Unconfigure)
• SPE (Serial Poll Enable)
• SPD (Serial Poll Disable)
There are other interface messages: listener-address, talk-address, and secondary commands.
Uni-line
messages
Address
commands
Universal
commands
IFC
REN
IDY
GTL
SDC
PPC
GET
TCT
LLO
DCL
PPU
SPE
SPD
Listener
address
Talker
address
Secondary
commands
Multi-line messages
The 2558A supports interface messages marked with a .
Note
Difference 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 a designation. Therefore, SDC messages are directed at a particular
instrument while DCL messages are directed at all instruments on the bus.
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