Logic Triggering
TDS 420A, TDS 430A, TDS 460A & TDS 510A User Manual
3–71
To choose the logic function you want applied to the input channels (see page
3–68 for definitions of the logic functions):
Press TRIGGER MENU
➞ Type (main) ➞ Logic (pop-up) ➞ Class (main) ➞
Pattern (pop-up)
➞ Define Logic (main) ➞ AND, OR, NAND, or NOR (side).
You can also time qualify a pattern logic trigger. That is, you specify a time that
the boolean logic function (AND, NAND, OR, or NOR) must be TRUE (logic
high). You also choose the type of time qualification (greater or less than the
time limit specified) as well as the time limit using the Trigger When menu
selection.
1. Press TRIGGER MENU
➞ Type (main) ➞ Logic (pop-up) ➞
Class
(main) ➞ Pattern (pop-up) ➞ Trigger When (main) ➞ True for less
than or True for more than
(side).
2. Use the general purpose knob or keypad to set the time in the side menu.
When you select True for less than and specify a time using the general purpose
knob, the input conditions you specify must drive the logic function high
(TRUE) for less than the time you specify. Conversely, True for more than
requires the boolean function to be TRUE for longer than the time you specify.
Note the position of the trigger indicator in Figure 3–37. Triggering occurs at the
point the logic function you specify is determined to be true within the time you
specify. The digitizing oscilloscope determines the trigger point in the following
manner:
It waits for the logic condition to become true.
It starts timing and waits for the logic function to become false.
It compares the times and, if the time TRUE is longer (for True for more
than) or shorter (for True for less than), then it triggers a waveform display
at the point the logic condition became false. This time can be, and usually
is, different from the time set for True for more than or True for less than.
In Figure 3–37, the delay between the vertical bar cursors is the time the logic
function is TRUE. Since this time is more (216 ms) than that set in the True for
more than menu item (150 ms), the oscilloscope issues the trigger at that point,
not at the point at which it has been true for 216 ms.
Define Logic
Define a Time Qualified
Pattern Trigger
To Next Page
Loading...
Need help?
General
