6.4. On-Chip Signal Quality Monitoring (Eye Viewer)
Eye Viewer uses a phase interpolator (PI) and sampler (SMP) to estimate the horizontal eye opening. Controlled by a logic generator, the PI generates a sampling clock and the SMP samples the data from the receiver output. The SMP outputs parallel data that is monitored for CRC or BER errors. When the PI output clock phase is shifted by small increments, the data error rate goes from high to low to high if the receiver is good. The number of steps of valid data is defined as the width of the eye. If none of the steps yield valid data, the width of the eye is equal to 0, which means the eye is closed.
The Transceiver Reconfiguration Controller provides an Avalon-MM user interface to enable the Eye Viewer feature.
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