Setting the Trigger
From tigwiki
WARNING: The triggering hardware, firmware and software was done by Paul Garrett. Ultimately, if you're having trouble, ask him.
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[edit] Trigger Implemented and Selected by 2365 ULM
The trigger logic is implemented in a series of Lecroy 2365 ULMs. These are programmable CAMAC logic modules with ECL inputs and ouptuts. A diagram showing the layout and cabling of these modules is given #Trigger Hardware and Firmware. All inputs and outputs are ECL. The actual triggering behavior depends on how the various ULMs are programmed. The ULMs are programmed at the beginning of a run as determined in the Front end code, Rebooting or Reloading the Front-End. This code checks the ODB mode, http://isdaq08.triumf.ca:8081/Equipment/Camac/Settings/Trigger/Mode?cmd=Set&exp=8pi, entry to determine how to program the ULMs.
[edit] ODB Entries
The trigger mode is controlled by the ODB under /Equipment/Camac/Settings/Trigger, http://isdaq08.triumf.ca:8081/Equipment/Camac/Settings/Trigger?exp=8pi.
The entry is called Mode, http://isdaq08.triumf.ca:8081/Equipment/Camac/Settings/Trigger/Mode?cmd=Set&exp=8pi.
The trigger mode can be set by directly setting the mode, http://isdaq08.triumf.ca:8081/Equipment/Camac/Settings/Trigger/Mode?cmd=Set&exp=8pi. You are also asked to set this mode at the beginning of a run.
[edit] What Are the Trigger Modes
NOTE: This is valid as of 04 August 2005.
The following is an excerpt from the frontend source code, Rebooting or Reloading the Front-End#Source Code for the Front-End Program that defines a numerical mode to several possible modes of operation. "G" means that the trigger requires a germanium; GG means two germaniums; B means beta counter (plastic scintillators); SI means sillicon. SC means downscaled. Two or more types of equipment together means "and"; an underscore _ means "or". (_SINGLE) and _COIN are leftovers from earlier versions.) So for example, in Mode 6, you would trigger on either a gamma-gamma coincidence or a gamma-beta coincidence, and as such, would collect all gamma-gamma coincidence events and all gamma-beta coincidence events; in Mode 7, you would acquire some fraction of single gammas, all gamma-gamma coincidences, some fraction of single betas, and all gamma-beta coincidences. Mode 0 accepts all singles on all streams -- betas, gammas, etc. It's really only useful for testing and some calibrations.
#define TEST_SINGLES (0) /* sends singles through on all */ #define G_SINGLE (1) #define GG_COIN (2) #define SCG_GG (3) #define G_GB (4) #define GB (5) #define GG_GB (6) #define SCG_GG_SCB_GB (7) #define GGB (8) #define GG_GGB (9) #define SCG_GG_GGB (10) #define BBaF (11) #define GBBaF (12) #define G_BBaF (13) #define SCG_GG_GB_BBaF (14) #define BaFBaF (15) #define BBaF_BaFBaF (16) #define BaFBaF_GBBaF (17) #define GBaFBaF (18) #define BaFBaF_GBaFBaF (19) #define SCG_GG_GBaFBaF (20) #define SI (21) #define SCG_GG_SI (22) #define GSI (23) #define GG_GSI (24) #define SCG_GG_GSI (25) #define BSI (26) #define SISI (27) #define GG_GSI_SISI (28) #define SCG_GG_GSI_SISI (29) #define SCG_GG_GSI_SISI_SCSI (30) #define SCG_GG_GSI_SISI_SCSI_BGSI_BSISI (31) #define SCG_GG_GSI_BGG_SI_BSI_BSCG (32) #define BGSI (33) #define SCG_GG_SI_BGG_BSI (34) #define G_SI_BG_BSI (35) #define SCG_GG_GSI_BGG_SCSI_SISI_BSI_BSCG (36) #define SCG_GG_GSI_SISI_SCSI_GBaFBaF_SIBaFBaF (37) #define GSIBaF (38) #define GBaF (39) #define SCG_GG_BGG_BGBaF_GBaFBaF (40) #define SCG_GG_BGBaF_GBaFBaF_SCSI_SISI_GSI (41) #define SCG_GG_BGG_BGBaF_GBaFBaF_BGSI (42) #define G_SI_BG_BSI_SCB (43) #define BG_BSI_SCB (44)
[edit] Trigger Hardware and Firmware
A circuit drawing for the trigger logic, along with an explanation of how the 2365 ULMs work, is shown in the diagram below. These modules are in Crate 2. The 2365 in N18 selects and routes possible hardware pretriggers -- singles, coincidences, and downscales -- from each of the Ge, Plastic, BaF, and Si subsystems. N19 simply inverts the "busy" signals for vetoing pre-triggers. N20 performs vetoing. N16 stretches the signals to about 1 us. The actual coincidence overlaps are typically done in N21. Some of the outputs for N21 (4-7) feed back to the inputs (12-15) to make more complicated triggers. Finally outputs 0-3 of N21 actually generate master triggers for each of the data streams.
Your best bet for understanding how the triggering works is to compare this logic diagram to some working Rebooting or Reloading the Front-End#Source Code for the Front-End Program for a specific trigger mode http://isdaq08.triumf.ca:8081/Equipment/Camac/Settings/Trigger/Mode?cmd=Set&exp=8pi Trigger 4 (Ge or Ge-Plastic Coincidence)
If you are having trouble reading this diagram, click Media:logic2.pdf to bring up a printable .pdf version on broswers so enabled.
Note an error on this diagram: The correct order in which the configuration is written to the module is: A0,B0,A1,B1,A2,B2...A7,B7,C,T
Note also that pretrigger (N18) inputs 5 and 6 are BaF singles and BaF-BaF coinc. respectively.
