DS92LV1224 Datasheet, PDF (13/16 Pages) National Semiconductor (TI) – 30-66 MHz 10 Bit Bus LVDS Deserializer

Application Information (Continued)
USING T_DJIT AND T_RNM TO VALIDATE SIGNAL
QUALITY
The parameters t_DJIT and t_RNM can be used to generate an
eye pattern mask to validate signal quality in an actual
application or in simulation.
The parameter t_DJIT measures the transmitter’s ability to
place data bits in the ideal position to be sampled by the
receiver. The typical t_DJIT parameter of −80 ps indicates that
the crossing point of the Tx data is 80 ps ahead of the ideal
crossing point. The t_DJIT(min) and t_DJIT(max) parameters
specify the earliest and latest, respectively, time that a cross-
ing will occur relative to the ideal position.
The parameter t_RNM is calculated by first measuring how
much of the ideal bit the receiver needs to ensure correct
sampling. After determining this amount, what remains of the
ideal bit that is available for external sources of noise is
called t_RNM. It is the offset from t_{DJIT(min or max)} for the test
mask within the eye opening.
The vertical limits of the mask are determined by the
DS92LV1224 receiver input threshold of +/− 50 mV.
Please refer to the eye mask pattern of Figure 11 for a
graphic representation of t_DJIT and t_RNM.
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FIGURE 11. Failsafe Biasing Setup
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FIGURE 12. Using t_DJIT and t_RNM to Generate an Eye Pattern Mask and Validate Signal Quality
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