2 General Description

2.6 Assumptions and dependencies

1. Incoming fragments may be of fixed size or of variable size depending on the sub-detector.

2. Incoming fragments contain flags which may be set if the ROD or front-end detects errors in the data before transmission to the ROB.

3. The Read-out Link between the ROD and the ROB is duplex, i.e. the ROB can send flow control and other signals back to the ROD.

4. The Level-2 Trigger and Level-3 Trigger can function if one or more ROBs do not respond to signals from them (e.g. RoI_request, L2_accept).

5. Front-end systems must preserve the trigger order at the input to the ROB. Each front-end must provide exactly one fragment for each trigger. A front-end must not ignore a trigger and must send a fragment (even if it is a null fragment).

6. Event_ID numbers will increment monotonically (i.e. they will not be random).

7. Header or trailer information in event fragments will not be compressed by the Front -End before transmission to the ROB.

8. Fragments will contain a start_of_event marker.

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