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11. FRAME + RARE PULSE
Demo: with:
DOX2025
DOX2040
DOX2100
DOX2xxxB
Test Signal
n°11 : Frame + Rare pulse
Nature
Digital clock signal with a fault
Specs
F clock ≈ 5 MHz, Vpp ≈ 3.3 V
Oscilloscope Settings
100 ns/div., then 25 ns/div. - MAIN = 500 mV/div. DC coupling
Trigger
DC coupling on MAIN, level ≈ 1.8 V
Modes
Triggered mode preferable - SPO mode, duration 1 or 2 s
Objectives
Capture and display of a rare fault in SPO mode
Triggering possible on pulse width < 20 ns, after SPO analysis
a) Adjust the oscilloscope so as to display the signal approximately (possible using the “Autoset” mode), then set the parameters as indicated opposite.
b) The signal displayed represents a digital clock at 100 ns.
By paying attention, it may be possible to spot a certain instability of some edges of the signal.
c) Enter Delayed mode with 10 ns/div. for the delayed time base.
The fault is rather rare, since it affects only one clock pulse in 1000.
It is a brief pulse, lasting less than 10 ns, on the negative-going edge of the clock pulse.
We are going to use triggering on pulse width < 20 ns by placing the triggering level on the top part of the clock pulse to achieve stable triggering
on the fault, then use the Delayed and LongMem mode to display the clock signal and the fault.
