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Chapter 4: Concepts
Understanding State Mode Sampling Positions
To position the setup/hold window (sampling position) within the data
valid window, a logic analyzer has an adjustable delay on each sampling
clock input (to position the setup/hold window for all the channels in a
pod).
Sample Position
Adjustments on
Individual Channels
Some logic analyzers let you adjust the position of the setup/hold
window (sampling position) on each channel. When you can make
sampling position adjustments on individual channels, you can make
the logic analyzer's setup/hold window smaller because you can correct
for the delay effects caused by the probe cables and the logic analyzer's
internal circuit board traces, and you are left with the setup/hold
requirements of the logic analyzer's internal sampling circuitry.
However, the process of manually positioning the setup/hold window
for each channel is time consuming. For each signal in the device under
test and each logic analyzer channel, you must measure the data valid
window in relation to the bus clock (with an oscilloscope), repeatedly
position the setup/hold window and run measurements to see if the
logic analyzer captures data correctly, and finally position the setup/
hold window in between the positions where data was captured
incorrectly.
In Agilent Technologies logic analyzers which have the eye finder
feature, you can automatically position the setup/hold window on each