User`s manual

Arming and Triggering Program Comments
The following information is associated with arming and triggering the
AFG. Included are details on the operation of the AFG’s arming and
triggering functions, and on the various modes, ranges, etc., used in the
programs in this chapter.
Reference
Oscillator Sources
There are five reference oscillator sources for the AFG which are selected
by the
[SOURce:]ROSCillator:SOURce command:
• CLK10 – The VXIbus CLK10 (10 MHz) line.
• EXTernal – The AFG’s front panel “Ref/Smpl In” BNC (TTL levels).
• ECLTrg0 or 1 – The VXIbus ECL trigger lines.
• INTernal[1] – The internal 42.94967296 MHz oscillator (default source).
• INTernal2 – The internal 40 MHz oscillator.
The
INTernal[1] reference oscillator is recommended for use with the
Direct-Digital-Synthesis (DDS) time base (
[SOURce:]FREQuency[1]
subsystem) for high resolution and frequency range. The INTernal2
reference oscillator is recommended for use with the divide-by-n time base
(
[SOURce:]FREQuency2 subsystem) to produce exact frequencies such as
10 MHz, 20 MHz, etc,.
AFG Frequency
Synthesis Modes
When outputting a fixed (continuous) frequency signal, the DDS time base
(
[SOURce:]FREQuency[1]) or the divide-by-N time base
(
[SOURce:]FREQuency2) are the most often used. In addition to these time
bases, other sources which can be selected with the
TRIGger[:STARt]:SOURce command are:
• BUS (the GPIB Group Execute Trigger (GET command) or the
IEEE-488.2
*TRG common command)
• ECLTrg0 or ECLTrg1 (the VXIbus ECL trigger lines)
• EXTernal (the AFG’s front panel “Ref/Smpl In” BNC)
• HOLD (suspends sample generation)
• INTernal[1] (the [SOURce:]FREQuency[1] subsystem DDS
frequency synthesis)
• INTernal2 (the [SOURce:]FREQuency2 subsystem Divide-by-n
frequency synthesis)
• TTLTrg0 through 7 (the VXIbus TTL trigger lines)
In programs where the time base (trigger source) is not specified, the default
DDS time base (
[SOURce:]FREQuency[1]) is used.
Chapter 5 Arming and Triggering 197