Commands - YOKOGAWA TA520 User Manual

1.5 Responses to Interface Messages
1.5 Responses to Interface Messages
What is an Interface Message?
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An interface message (also called an interface command or bus command) is issued by
the controller. Interface messages are classified as follows.
Uni-line messages
Messages are transferred through a single control line. The following three types of uni-
line message are available.
• IFC (Interface Clear)
• REN (Remote Enable)
• IDY (Identify)
Multi-line messages
Eight data lines are used to transmit a message. Multi-line messages are classified as
follows.
Address commands
Valid when a piece of equipment is designated as a listener or a talker. The following
five address commands are available.
• Commands valid for pieces of equipment designated as listeners
GTL (Go To Local)
SDC (Selected Device Clear)
PPC (Parallel Poll Configure)
GET (Group Execute Trigger)
• Command valid for pieces of equipment designated as talkers
TCT (Take Control)
Universal commands
Valid for any item of equipment, irrespective of whether the item is designated as a
listener or a talker. The following five universal commands are available.
LLO (Local Lockout)
DCL (Device Clear)
PPU (Parallel Poll Unconfigure)
SPE (Serial Poll Enable)
SPD (Serial Poll Disable)
In addition to the above commands, a listener address, talker address or secondary
command can be sent in an interface message.
Differences between SDC and DCL
The SDC command is an address command and requires that both the talker and
listener be designated. DCL is a universal command and does not require that the
talker and listener be designated. Hence, SDC is used for specific items of equipment,
while DCL can be used for any equipment connected to the communications bus.
IM 704310-12E