Keithley 2002, Getting Started Manual, Page: 37 / 95

Trigger model layers
The trigger model has three layers: the Arm Layer, Scan Layer and Measure Layer. For IEEE-
488 bus operation, these layers are known as Arm Layer 1, Arm Layer 2 and the Trigger Layer.
Once the Model 2002 is taken out of idle, operation proceeds through the layers of the trigger
model down to the device action where a measurement occurs.
Control source
In general, each layer contains a control source which holds up operation until the pro-
grammed event occurs. The control sources are described as follows:
• Immediate –Event detection is immediately satisfied, allowing operation to continue.
• Manual – Event detection is satisfied by pressing the TRIG key.
• GPIB – Event detection is satisfied when a bus trigger (GET or *TRG) is received.
• RT-Clock – Event detection in the Arm Layer is satisfied when the programmed time and
date occur. (Not available in the Scan Layer and Measure Layer.)
• Timer – Event detection is immediately satisfied on the initial pass through the layer.
Each subsequent detection is satisfied when the programmed timer interval elapses. (Not
available in the Arm Layer.)
• External – Event detection is satisfied when an input trigger via the EXTERNAL TRIG-
GER connector is received.
• TrigLink – Event detection is satisfied when an input trigger via the TRIGGER LINK is
received.
• Hold – With this selection, event detection is not satisfied by any of the above con-
trol source events and operation is held up.
2-12 Measurement Options