Run Control

Introduction

• Implemented as a ``concurrent hierarchical state machine'' (CHSM).
• Tree of run controllers, where each node in the tree can either control a set of child controllers or some bit of the ATLAS readout system (or both?).
• Communication is only between parent and child, not between children at the same level.
• Limited synchronisation between different activities can be provided using extra controllers in the tree and altering the order in which the child state transitions are executed.
• Each state transition is associated with a set of actions (one method per transition) returning success or failure.
• Parent executes its actions. If successful its state has changed (but is still locked) and it then asks its children to perform their actions. If all child actions are successful the parent transition has completed successfully. Otherwise the parent sets a (concurrent) error state.
• The main states are Initial, Loaded, Configured, Running and Paused. There are also error states.
• The main transitions are sequentially between those states, ie load, configure, start, pause, resume, stop, unconfigure, unload, terminate.