4.3. NSCLDAQ version 11 format

Contains the size of the body header. Note that this allows application specific data to be appended to the body header as the formatting software uses this size to determine both the presence of and size of this header.

If a s_size is larger than sizeof(v11::BodyHeader) the body header is said to have a Body Header Extension.

In version 11, if s_size is 0, the item has no body header.

The timestamp at which the item was produced. The units of the timestamp are application defined, however it is critical that all data sources have the same timestamp units, the same source of timestamp increments, and as close to the same zero time as electronically possible.

The data source. Each data source is assumed, by the event builder, to be totally time ordered. The process of event building is, therefore, oneo f merging the times from all data sources to produce a single totally time ordered stream of fragments and then gluing (glomming) together fragments whose timestamps are within a specified coincidence window.

Data sources must be unique and often, but not always, identify a readout program. As a counter example to this, a VME crate with CAEN DPP Modules is readout with each module as a separate data source.

NSCLDAQ's event builder provides for rough barrier synchronization between data sources. Barrier synchronization means that no further data is emitted from a source within the event builder until all sources have, a the head of their output queues, a barrier item.

If s_barrier, is non-zero, barrier synchronization is triggered. The s_barrier value may carry additional information about why barrier synchronization is underway.