User manual

Basically, the IEEE-488 bus is simply a communication system between two or more elec-
tronic devices. A device can be either an instrument or a computer. When a computer is
used on the bus, it serves to supervise the communication exchange between all the devices
and is known as the controller. Supervision by the controller consists of determining which
device will talk and which device will listen. As a talker, a device will output information and
as a listener, a device will receive information. To simplify the task of keeping track of the
devices, a unique address number is assigned to each one.
On the bus, only one device can talk at a time and is addressed to talk by the controller.
The device that is talking is known as the active talker. The devices that need to listen to the
talker are addressed to listen by the controller. Each listener is then referred to as an active
listener. Devices that do not need to listen are instructed to unlisten. The reason for the un
-
listen instruction is to optimize the speed of bus information transfer since the task of listen-
ing takes up bus time.
IEEE-488 Bus Overview
2000-900 (J - Aug 2010) BOOK.fm Page 2 Wednesday, October 12, 2011 12:29 PM