Appendix D
Operation of the GPIB
© National Instruments Corp.
D-3
GPIB-232CT User Manual
The Controller-In-Charge and System Controller
Although there can be multiple Controllers on the GPIB, 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 board is usually the System Controller in S mode and 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
