This subprocessor calculates the time since last hit (TSLH) of each PMT in every event. The RAA is best suited to this task as strict time ordering of events simplifies this process considerably.
The subprocessor's primary role is to calculate TSLH and pack this information into an extended zdab structure for future use. It can be used, however, to simply place TSLH into the data structure for analysis in the same job. This functionality is controlled by the first word in bank RAAS 10. If this word is 0, the subprocessor will simply pack the new data into a zdab. If this word is 1, TSLH will be written to the data structure. A value of 2 will do both.
The subprocessor is intended to be used in isolation from other RAA subprocessors. In practice, any processing in the same job should only be done after the restore phase of the RAA.
It is not necessary (and not recommended) to call UPK when using this subprocessor. UPK is called directly by the subprocessor in the RAA restore phase. If the user does call UPK explicitly from the PEL, the subprocessor will not override the user's PEL, but this could lead to the RAA temp file becoming too large.
The subprocessor's output is not affected by run or subrun boundaries but the first few events it processes in any job will have an unknown TSLH. To avoid this problem, specify the previous sub run as the first file to be inputted and use the skip command to only process the last few events. A filter can then be used after the RAA restore phase to select only the events required.
To determine the approximate number of events in a sub run, use the unix command:
od -s4 zdab_name.zdab | grep ZDAB -c
The TSLH data word is word 16 of the PMT (or equivalent) banks. Bit 1 in the status word of the EV bank is set if TSLH information is present.