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Reference
3-26 GB1400 User Manual
Input Decision Threshold
The input decision thresholds of the DATA, and REF DATA inputs can be
independently adjusted. However, it is important to note that input threshold
adjustment applies only for single-ended operation. When operating Analyzer
data inputs in the differential mode, their input decision threshold effectively
becomes the average of the positive peak and negative peak voltage levels and is
not adjustable by the user.
Procedure to Adjust (Single-ended) Input Decision Threshold:
1. Verify that the selected input is set up for singled-ended operation. For
DATA operation, connect a cable from rear panel threshold to front NOT-
DATA (DATA-BAR) input.
2. Select either the DATA, CLOCK, or REF DATA input using the F2 and F3
keys.
3. Press the THRESH key. Verify that its LED turns on.
4. Press the input up/down keys while observing selected threshold value in the
bottom, right field of the display. Decision threshold setup range is a function
of input termination as shown in table below.
Table 3-8. Input Threshold Range as a Function of Termination
Selected Termination Threshold Setup Range
GND - 1.5 to + 1.0 VDC, 50 mV steps
- 2 V - 2.5 to + 0.0 VDC, 50 mV steps
AC - 1.5 to + 1.0 VDC, 50 mV steps
The displayed threshold takes effect immediately. In other WORDs, threshold is
incremented or decremented each time you press the up or down key. Note that
threshold is an AUTO SEARCH parameter. So be sure turn off AUTO SEARCH
if you want to fix delay at a specific value.
Logically Inverting Input Data
The INPUT section INVERT key may be used to logically invert the input data
pattern, that is change all 1s to 0s and 0s to 1s. If the INVERT key is off, then the
input data pattern is not inverted. However if the INVERT key is on, the input
data pattern is logically inverted. You can toggle input data inversion on or off by
pressing the INVERT DATA key. Note that logically inverting the input pattern
is equivalent to swapping the connections to the DATA and DATA-BAR inputs.
To toggle input data inversion on or off, press the INVERT key.