GPIB Interface Management Lines
The following table summarizes the GPIB interface management lines.
| Line | Description |
| ATN (attention) |
Controller drives ATN true when it sends commands and false when it sends data messages. |
| IFC (interface clear) |
System Controller drives the IFC line to initialize the bus and make itself CIC. |
| REN (remote enable) |
System Controller drives the REN line to place devices in remote or local program mode. |
| SRQ (service request) |
Any device can drive the SRQ line to asynchronously request service from the Controller. |
| EOI (end or identify) |
Talker uses the EOI line to mark the end of a data message. Controller uses the EOI line when it conducts a parallel poll. |