Synchronisation

There are a few cases where we will require synchronisation between actions in different crates. Specifically, some actions must either precede or follow other actions. These requirements dictate the hierarchy of controllers we will need. While it would be possible to use a different hierarchy for different situations, eg calibration runs, it would be most desirable if the same hierarchy could be used in all cases.

The following actions require synchronisation:

• Configure step: TTC broadcasts to initiate LVDS synchronisation should ideally be done before VME actions in the affected crates.
• Start step: loading of playback memories and switch into playback mode must be done before the TTC broadcast to start synchronous playback from all modules (of a given type) in the system.
• Start step: TTC broadcast to start synchronous playback must be before triggers are enabled.
• Start step: configuration of all processor crates should be complete before the overall BUSY is removed. Q: within PP crates, is there an ordering required between PPMs and PPRODs?
• Start step: configuration of all processor crates must be complete before triggers are enabled. For local triggers this is easy as we enable our triggers via the TTCvi. For CTP and calorimeter calibration triggers however, we rely on the BUSY signal to veto triggers.
• Stop step: triggers should be disabled before playback mode is switched off.

Some other possibilities include:

• Start step: configuration of processor modules before/after RODs? Eg CP/JEP crates before/after ROD crates; PPMs before/after PPRODs in the same crate.