315
6. The Clock Edge determines whether the instrument finds
the trigger point on the rising edge (left button) or the
falling edge (right button) of the clock signal. Click a
Clock Edge button.
Set the data and clock
levels
7. To set the data transition level, click Data Level, and use the
multipurpose knobs or pop-up keypad to set the value.
8. The instrument uses the clock level to determine when a
clock edge occurs. The point the clock crosses the clock
level is the reference point from which it measures setup
and hold time settings. To set the clock threshold level, click
Clock Level and use the multipurpose knobs or pop-up
keypad to set the value.
Both Clock and Data Levels can be set to a value appropriate to
either the TTL or ECL logic families by clicking TTL or ECL on
the Level pop-up keypad.
Set the setup and hold
times
9. Click Setup Time, and use the multipurpose knob or pop-up
keypad to set the setup time relative to the clock.
10. Click Hold Time, and use the multipurpose knob or pop-up
keypad to set the hold time relative to the clock.
Positive setup time always leads the clock edge; positive
hold time always follows the clock edge. Setup time always
leads the hold time by at least 2 ns (TS + TH.≥ 2 ns).
Attempting to set either time to reduce the 2 ns limit adjusts
the other time to maintain the limit.
See the figure below for an example of a setup and hold
violation trigger.
In most cases, you will enter positive values for both setup and
hold time. Positive values set the instrument to trigger if the data
source is still settling inside the setup time before the clock or if it
switches inside the hold time after the clock. You can skew this
setup/hold violation zone by entering negative values as shown
below:
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