Logic Triggering
Reference
Mode & Holdoff
You can change the holdoff time and select the trigger mode using this menu
item.
1. Press TRIGGER MENU ➞ Type (main) ➞ Logic (pop-up) ➞
Class (main) ➞ Pattern or State (pop-up) ➞ Mode & Holdoff (main) ➞
Auto or Normal (side).
In Auto mode the oscilloscope acquires a waveform after a specific
time has elapsed even if a trigger does not occur. The amount of time
the oscilloscope waits depends on the time base setting.
In Normal mode the oscilloscope acquires a waveform only if there is
a valid trigger.
2. Press Holdoff (side). Enter the value in percent using the general pur-
pose knob or the keypad.
Depending on whether you chose the class Pattern or State, there are differ-
ent menus for defining the channel inputs and the combinational logic.
When you select Pattern, the oscilloscope will trigger on a specified logic
combination of the four input channels. See page 3-80 for details on opera-
tions common to both pattern and state triggers.

Define Inputs

To set the logic state for each of the input channels (Ch1, Ch2, ...):
1. Press TRIGGER MENU ➞ Type (main) ➞ Logic (pop-up) ➞
Class (main) ➞ Pattern (pop-up) ➞ Define Inputs (main) ➞ Ch1, Ch2,
Ch3, or Ch4 (side). (On the TDS 620A & TDS 524A, Ch3 and Ch4 are
replaced by Ax1 and Ax2.)
2. Repeatedly press each input selected in step 1 to choose either High (

H

),
Low (
L
), or Don’t Care (
X
) for each channel.

Define Logic

To choose the logic function you want applied to the input channels (see page
3-79 for definitions of the logic functions for both pattern and state triggers):
Press TRIGGER MENU ➞ Type (main) ➞ Logic (pop-up) ➞ Class (main) ➞
Pattern (pop-up) ➞ Define Logic (main) ➞ AND, OR, NAND, or NOR (side).
Pattern Operations