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This screen provides access to all controls for configuring a single channel of DAC output. The following PVs can be set here (all All PVs on this screen are prefixed with $(device):$(axis)):. Three groups of PVs are shown. First the graph at the top.
| Name | PV | Description |
|---|---|---|
| DAC Compensation Pre-Emphasis Filter | :DAC:FILTER_S | This filter is applied to the generated bunch stream immediately before transmission to the DAC and can be used as a pre-emphasis filter to correct for amplifier artefacts. The valid range of taps is +-1±1, and the response of the filter should be adjusted to avoid overflow: this will be indicated by the DAC FIR overflow PV :DAC:FIR_OVF. |
On the left PVs controlling and monitoring the output stream. See Guide to MBF Signal Processing for more details of the overflows.
| Name | PV | Description |
|---|---|---|
| FIR early clipping | :DAC:BUN_OVF | If FIR gain is set high then the FIR output may be clipped at an early stage in output processing. |
| Output overflow | :DAC:MUX_OVF | This event occurs if the DAC output has overflowed before output to the pre-emphasis filter. |
| Preemph overflow | :DAC:FIR_OVF | This event indicates overflow in the DAC pre-emphasis filter. |
| Output delay | :DAC:DELAY_S | This is used to delay the DAC output so that the closed loop delay is a single machine revolution.The output delay on each DAC output should be configured to ensure that the complete closed loop delay of the MBF processing system (including all external signals) is exactly equal to one machine revolution. Note that this delay changes each time a new version of the firmware is released. |
| Output enable | :DAC:ENABLE_S | Enables output This control determines whether any signal is driven to the output DAC. When the MBF control IOC is restarted this is automatically set to "Off". |
On the right the DRAM and MMS sources are controlled.
| Name | PV | Description | |
|---|---|---|---|
| MMS input | :DAC:MMS_SOURCE_S | Min/Max/Sum data can be sourced from before or after the pre-emphasis filter . | DRAMor from the feedback FIR stream. This last option is sourced after bunch by bunch gain adjustment but before output enable for this stream. |
| MMS | Link to Min/Max/Sum screen for DAC. | ||
| Memory input | :DAC:DRAM_SOURCE_S | Data capture to memory can be sourced from before or after the pre-emphasis filter. |
The three event indicators are as follows:
| Name | PV | Description | |||||
|---|---|---|---|---|---|---|---|
| DAC bunch FIR overflow | :DAC:BUNMMS_OVF | Shows This shows an alarm state if the current bunch-by-bunch FIR gain results in overflow for a bunch selected for output. | DAC output overflowfeedback FIR stream, as selectable as one of the MMS inputs, sees an overflow. This alarm will be shown even if this stream is being ignored. | ||||
| Event | :DAC: | MUXEVENT_LIMIT_ | OVFShows an alarm state if the combination of DAC outputs selected by the active bank control results in overflow. | DAC FIR overflow | :DAC:FIR_OVF | Shows an alarm state if overflow occurs in the pre-emphasis filterS | This should be set to a number in the range 0..1 to select the bunch motion threshold used to generate the ADC min/max event. This is generated whenever bunch motion exceeds the programmed limit and can be used to generate a trigger event. |
| DAC min/max event | :DAC:EVENT | Indicates that a bunch min/max event as configured by :EVENT_LIMIT_S has been seen. Note that this event is created as part of the Min/Max/Sum processing, so the MMS input :MMS_SOURCE_S will affect which events are seen. |