PVs

This page describes the data held by each PV served by this IOC.

BEGINRUNEX

This is used for starting a run.

Setting this PV to 1 triggers an event which firstly starts the hardware by setting the run status register’s lowest bit to 1, then sends a run start to Kafka. If either of those two fail, the put will error.

ENDRUN

This is used for ending a run.

Setting this PV to 1 triggers an event which firstly stops the hardware by setting the run status register’s lowest bit to 0, then sends a run stop to Kafka. If either of those two fail, the put will error.

DAETIMINGSOURCE / DAETIMINGSOURCE:SP

These PVs respectively display the status of and set the streaming control board’s timing source (or frame_sync_select as named by its register) The options are:

• INTERNAL_TEST_CLOCK: The streaming control board uses it’s internal clock to mark the beginning of new frames, without synchronizing with any external signals. This is useful for testing when an external timing source is not present, but is not useful for scientific data collections.

• ISIS: This synchronizes with the ISIS accelerator timing pulse.

• SMP: This synchronizes to an external timing pulse, usually from a chopper.

• UNKNOWN: The timing source is unknown – the hardware is in a strange state.

HWRUNNING

This PV indicates whether the hardware is running or not, as determined by the status register (in particular the 0x20 bit-flag)

TITLE / USERS

These are just “soft” PVs used for forming the run starts and stops

RUNNUMBER / IRUNNUMBER

These are the current run number. A run stop increments these. They are read-only from EPICS, but changing the State file can update them.