Attention. One of the management lines for GPIB.
ATN line is used in data mode, which is used to transfer data between devices, and command mode, which is used to send commands to each device from the controller.
ATN line indicates the current state of the data lines.
ATN line is managed by the controller.
When ATN line is low, the bus is in command mode and each device is required to receive a command from the controller.
When ATN line is high, the bus is in data mode which is used for sending and receiving measurement data.