Datasheet

Application Note
www.tektronix.com/bench12
Figure 24 shows the MSO triggered on the rising edge of the
input to the ADC. The unique front panel Wave Inspector
®
navigation controls are used to zoom to 20 X magnification
around the trigger, allowing the parallel bus decode values
to be easily seen. The ADC data is stable at the falling clock
edge and the MSO decodes the bus values at the falling edge
of the clock. Therefore, the parallel bus updates at the falling
clock edge when the ADC data is stable.
The MSO’s powerful triggering finds signal faults and triggers
on parallel or serial bus content to focus the acquisition on
problem areas. However, once the data is acquired, triggering
doesn’t apply any more. Manually searching through long
record lengths can be a frustrating and time-consuming
process. A 10 Mpoint waveform record is over 10,000 full
resolution screens of data. It takes over two hours and forty
five minutes to scroll through a 10 Mpoint waveform at the rate
of one full resolution screen per second. Whereas using Wave
Inspector to search and mark a 10 Mpoint record 6-bit data
bus acquisition takes about 30 seconds. Once the data has
been found and marked, navigating between occurrences is
as simple as pressing the front-panel Previous and Next arrow
buttons. Searches are also available for trigger types such
as edges, pulse widths, runt, setup/hold times, logic, rise/fall
times and bus data values.
Figure 25 shows Wave Inspector searched the ADC parallel
bus for 00 hex value which should be at each test ramp signal
valley. But, no 00 hex values are found as indicated by the lack
of white triangle search marks at the top of the display and as
indicated by the search events readout showing zero at the
bottom of the display. No 00 hex values means that the
ADC did not see the analog input voltage that correspond
to a 00 hex value. The acquisition system analog signal
conditioning circuit did not correctly process the minimum
peaks of the test ramp signal to match the minimum ADC
input voltage in order for the ADC to produce a 00 hex output.
Figure 25. Wave Inspector search finds no 00 hex values at test signal valleys. Figure 24. The MSO triggered on the rising edge of the input to the ADC and Wave
Inspector zooms in so that parallel bus decode hex values are easily seen. The test
ramp signal is on channel one. At the bottom of the display is the ADC clock on digital
channel zero. The ADC digital output bus signals one through six are above the clock
waveform. The ADC digital signals are grouped together into the clocked parallel bus at
the center of the display.