Tektronix 071-0590-00 user manual Input Decision Threshold, Logically Inverting Input Data

Reference

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.

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