The E852 pulser trigger is derived from the system pulser and is controlled by two switches: pulser on/off and free_run on/off.
With the pulser switch on, the system pulser is sent to the top of the MPS where it generates a pretrigger and a beam.dt signal and sends them to the fast trailer. The relative timing of beam.dt and pretrigger at the fast trailer is the same as for "real" physics triggers.
The pretrigger signal arriving in the fast trailer strobes the beam PWC, gates the TPX's etc. exactly like the pretrigger in a physics trigger.
The pulser switch on also disables the S discriminator (S0.5, S2, S3) on top ofthe MPS and disables the 4413 discriminator (EV/BV/C1-C3) as well. This prevents pulser and "real" pretriggers from being present simultaneously.
Pulser switch on also generates a level 1 trigger at the same relative time as the "real" level 1 trigger. This is to insure lev_1 triggers when the level _1 mlu's are dissabled or are loaded with logic more complicated than a simple feed-through of ther strobe.
The free_run switch on dissables the DAQ busy, and it also generates an SSP0 signal at roughly the same time as the"real" SSP0 signal.
Note that there also is a MAMM bypass switch . The level_2 trigger mlu's are strobed by the MAMM_done signal from the LGD trigger processor. With this switch on, the MAMM_done is generated from the system pulser. See the MAMM strobe diagram.
To see a diagram click here//end file