1. Jianchun Wang1 Trigger Pocket  Trigger pocket contains trigger count (12bits) and BCO count (16bits).  It is generated and combined with pixel hit data at the router. When the router hangs, the trigger pockets are not recorded, results in missing trigger counts.  Trigger count at the router has 12 bits. The higher bits are assigned at online code, which can be wrong due to the missing counts. BlockStartEndLengthJump* 10646596 216144174257604 350225059383712 487728849783784 … 13368104147346643935 144540945458503914 … 19652426983145904059 20738917417628697 21742747435986  To match trigger pockets with Velo events, the trigger pockets are grouped into blocks with continuous trigger counts. In this way the BCO counts can be used to solve the ambiguity. File: xxx_080630_173421 All 9 files

2. Jianchun Wang2 Matching BCOs BlockOffsetTotalMatched Within Window MP  BCO 1065 1717 240964257 41451497 3819238 322145 4819278 289... 13163844664 44384073 141638450 3129 … 19204804590458144093409 2020480286 117 112457686 2645 File: xxx_080630_173421 Event ID  BCO 36810 - 36826 3320 - 3323 36827 - 41264 4072 - 4075 41265 - 41473 228 - 231 BCO within a block changes, i.e. BCO changes without reset. On of the cleanest runs.

3. Jianchun Wang3 First Matching For the first round of matching, I require that the block has at least 20 events and 50% of them matching with VELO BCO. I take only well matched events. With this, 55% of trigger pockets find their matches. Next step is to use already matched ones to constraint the rest pockets. Matched / Total

4. Jianchun Wang4 Special Features Observed  There are many single jumps regardless of even or odd trigger number.  Same trigger count repeated.  BCO changes without reset.  A small portion of triggered Velo events are missing. The event trigger count seems correct judging from this matching study. So it is of less problem. Maybe Marina can bring this issue to VELO meeting.  I will suggest Bruce to add more event trigger bits. That will make matching easier.