This screen is used to manage the Tune Phase Locked Loop functionality. For this to work the tune PLL NCO must be driven to the bunches to be measured, and the tune PLL detector must be configured to measure the same bunches. Then once the appropriate phase has been identified as set as the target phase, the frequency of the NCO will be driven to keep the measured phase.
The PVs here are divided into a number of groups. All PVs are prefixed with $(device):$(axis).
NCO
This group includes the readback waveform at the top. All the PVs in this group directly affect or measure the frequency generated by the tune PLL NCO.
| Name | PV | Description |
|---|---|---|
| Tune Following Frequency | :PLL:NCO:OFFSETWF | This waveform records the complete history of the Tune PLL offset frequency |
| Offset FIFO readout overrun | :PLL:NCO:FIFO_OVF | This will report an alarm status if the OFFSETWF waveform overruns. Typically this can happen if the detector dwell time is set too low. |
| Reset FIFO | :PLL:NCO:RESET_FIFO_S | This will force the OFFSETWF to discard any partially captured data. This is used to ensure that the next update received for MEAN_OFFSET is fully up to date. |
| Freq | :PLL:NCO:FREQ_S | When written this will set the PLL NCO to the given frequency. If feedback is running the offset will briefly be forced to zero. |
:PLL:NCO:FREQ | This reads back the current NCO frequency. This PV updates at 10Hz. | |
| Offset | :PLL:NCO:OFFSET | This is the current PLL offset, updated at 10Hz. |
| Gain | :PLL:NCO:GAIN_S | The NCO signal strength is configured here. |
:PLL:NCO:ENABLE_S | This PV turns the NCO output on or off. | |
| Mean | :PLL:NCO:MEAN_OFFSET | This is the mean offset computed over the last full OFFSETWF waveform. |
| Std | :PLL:NCO:STD_OFFSET | This is the standard deviation computed over the last full OFFSETWF waveform. |
| Tune | :PLL:NCO:TUNE | This is the fractional tune computed from the MEAN_OFFSET value and the base frequency. This PV updates when MEAN_OFFSET updates, and is forced to NaN when feedback is not running. |