Agilent Technologies L4400 - Manual (Page 87)

Operating and Programming 3
L4400 User’s Guide 75
Note: To stop a scan, send the ABORt command.
Externally Triggering a Scan
In this configuration, the instrument sweeps through the scan list once
each time a low- going TTL pulse is received on the rear- panel Ext Trig
Input line (pin 6).
• You can specify a scan count which sets the number of external pulses
the instrument will accept before terminating the scan. See “Trigger
Count” for more information.
• If the instrument receives an external trigger before it is ready to
accept one, it will buffer one trigger and then ignore any additional
triggers received (no error is generated).
• All readings from the scan are stored in volatile memory.

Readings accumulate in memory until the scan is terminated

(until the scan count is reached or until you abort the scan).
• Mx+B scaling and alarm limits are applied to measurements during
the scan and all data is stored in volatile memory.
The following program segment configures the instrument for an external
scan.

TRIG:SOURCE EXT

TRIG:COUNT 2

INIT
Select external mode

Sweep the scan list 2 times

Initiate the scan
Note: To stop a scan, send the ABORt command.
Trigger Count
Usage:
• L4421A 40- Channel Armature Multiplexer
• L4450A 64- Bit Digital I/O (digital input, counter channels only)
• L4452A Multifunction Module (digital input, totalizer channels
only)
You can specify the number of triggers that will be accepted by an
instrument before returning to the “idle” state. The trigger count applies
to both scanning and non- scanning applications.
• Select a trigger count between 1 and 500,000 triggers, or continuous.