Overview of E949 trigger system operation

Loading the trigger

A) From the host, a command is issued to PPC01:
 trig $TRIG_INIT
  
  --> TriggerLoad(pa,$TRIG_INIT)
     o Read a block of 12 words from the SSP (pa) into buffer
       MarkerData.
       Extract sspMarkerSize = MarkerData[0]
               tt_rr1_address = MarkerData[1];
               tt_rr2_address = MarkerData[2];


       Block MarkerData is written back to SSP; it contains: 
           Total word count (read from SSP)
           + 2 addresses (read from SSP)
           + and/or word (1 word read from file $TRIG_FILES/.andor) 
           + ps words (35 words read from file $TRIG_INIT)
           + dwf words (48 words read from file $TRIG_FILES/.dwf)
           + hextant cut words (64 words read from file $TRIG_FILES/.tt.hex)

       16384 words read from file $TRIG_FILES/.tt.rr1 contain
       refined range mask 1 data and are written to SSP address tt_rr1_address

       8192 words read from file $TRIG_FILES/.tt.rr2 contain
       refined range mask 2 data and are written to SSP address tt_rr2_address

* Note 1 - all 3 blocks are written and read back for checking
* Note 2 - Only file $TrigFilename contains an exclusive word count
           in the first line of the file. The size in the other files
           is hardcoded. There is no check that the file is the right size.
* Note 3 - Only the data in file $TRIG_INIT is expected to change
           and this filename is recorded in the database and in the
           comments in the data file at BeginRun. 

   --> TriggerInit(pa)
       o Send command TRSU to SSP(pa)
       o Wait for completion of command - Check SSP return code (4 ASCII char)
         SUCC - success
         INSQ - error initializing sequencer
         RBSQ - error reading back group register from sequencer
         INPS - error initializing prescaler
         RBPS - error reading back prescaler
         IDWF - error initializing delay-width-fanout
         TTIW - error writing trigger transmitter
         TTIR - error reading trigger transmitter
         THEX - error in readback of hextant data
         TRR1 - error in readback of refined range 1 data
         TRR2 - error in readback of refined range 2 data
         INAO - error loading and/or board association register

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