Appendix F
GPIB Basics
©
National Instruments Corporation
F-3
In G mode, the GPIB-232/485CT-A acts as a GPIB device. It performs only
the following two roles:
•
Talker—to send data to the GPIB host
•
Listener—to receive data from the GPIB host
The Controller-In-Charge and System Controller
Although the GPIB can have multiple Controllers, only one Controller at a
time is active, or Controller-In-Charge (CIC). Active control can be passed
from the current CIC to an idle Controller. Only one device on the bus, the
System Controller, can make itself the CIC. The GPIB interface is usually
the System Controller in S mode, but it is never the System Controller in
G mode.
GPIB Signals and Lines
The interface system consists of 16 signal lines and 8 ground return or
shield drain lines.
The 16 signal lines are divided into the following three groups:
•
Eight data lines
•
Three handshake lines
•
Five interface management lines
