8 Trigger
8.1 Trigger
Field Two. Field One is viewed as having 263 lines (or 313 lines) and Field Two is
viewed as having 262 lines (or 312 lines).
For the 525-line NTSC video standard, we refer to TV lines as follows (these are the
Field Modes):
–
Entire Frame, lines 1 to 525
–
Field One, lines 1 to 263
–
Field Two, lines 1 to 262 (note that this really refers to "actual" lines 264 to 525)
For the 625-line PAL and SECAM video standards, we refer to TV lines as follows:
–
Entire Frame, lines 1 to 625
–
Field One, lines 1 to 313
–
Field Two, lines 314 to 625
As the Field is changed, the appropriate value for Line is chosen to keep triggering
on the same line as before, or if this is not possible, the corresponding line in the
new Field. For example, suppose line 264 is selected while in the NTSC-M standard
and the Entire Frame mode. This is the first line in Field Two. If Field Two is then
selected, the Line number changes to Line 1, the same actual line in the TV signal. If
Field One is then selected, the line number stays at 1, but now we are triggering in
the first line in Field One. The only exception to this is if we are on the last line of
Field One and change to Field Two. In this case, we go to the last line in Field Two.
8.1.1.12 I/Q Mag
When I/Q Mag is selected, the trigger condition is met when the I/Q magnitude
crosses the I/Q magnitude trigger level. The magnitude is measured at the output of
the main I/Q digital receiver.
This trigger type is only valid for measurements that support the I/Q inputs.
The Trigger tab contains the following Trigger Source dependent controls when I/Q
Mag Trigger is selected:
–
"Prot Frame Aligned" on page 2660
–
"Trigger Delay" on page 2663
–
"Trigger Slope" on page 2667
Additional controls are also present that are not dependent on the selected Trigger
Source.
2655 Spectrum Analyzer Mode User's &Programmer's Reference
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