Appendix C Introduction to the GPIB
Attention (ATN)
When the ATN line is asserted, all devices become Listeners and participate in the communication. ATN signifies that a GPIB command message or data message is present on the data lines. When ATN is unasserted, information on the bus is interpreted as a data message. When ATN is asserted, information on the bus is interpreted as a
command message.
Attention
(ATN)
• Notifies devices of current data type.
• Is asserted by Controller-In-Charge.
Controller
ATN asserted
Command messages
Talker
ATN unasserted
Data messages
– 300.0005 V
All
Devices
Listener(s)
© National Instruments Corp.
C-9 TNT4882 Programmer Reference
