# UI-UI

The UI-UI measurement measures the difference of two consecutive N-UI measurements. The measurement then moves over one UI and measures the difference of the next N-UIs. This is analogous to the Period-Period jitter measurement, but measures unit intervals instead of periods.

There are two modes that can be used to calculate the data width:

- In Automatic mode, the data rate is found by searching your waveform for the narrowest data pulse. When the Automatic mode has trouble finding the data rate due to excessive high-frequency jitter on the waveform, the Semi Automatic mode can be used.
- In the Semi Automatic mode, Infiniium starts by searching around the Nominal Data Rate that you specify then automatically finds the data rate.

When measuring over the waveform, the UI-UI measurement is made on all the cycles of the waveform including any cycles that are not in the waveform window. When measuring in a region, the UI-UI measurement is made on all the cycles inside the region only.

## Configurable Measurement Parameters

This measurement is affected by the following settings (choose Measure > Thresholds...):

- Thresholds tab

## To measure

1. Click the toolbar's Data tab.
2. Click the UI-UI button.
3. Select the signal on which to make the measurement.
4. Select the Region in which to make the measurement:
   - Displayed Waveform — is what you see in the waveform window (which can be a zoomed-in view of the complete waveform).
   - Entire Waveform — specifies the complete waveform.
   - Region N — If regions are enabled for the selected signal, you can select one of those regions.
5. Enter the Number of UI (N) number of N consecutive intervals.
6. Select the Data Width Calculation as either Automatic or Semi Automatic.
7. If the Data Width Calculation is Semi Automatic, specify the Nominal Data Rate for the selected signal.
8. Click Apply.

## SCPI Command

`:MEASure:DATA:UUINterval`