class Decoder::THaCodaDecoder: public THaEvData

 To get the prescale factors for trigger number "trigger_type"
 (valid types are 1,2,3...)

 Public interface to decode the event.  Note, LoadEvent()
 MUST be called once per event BEFORE you can extract
 information about the event.

 Main engine for decoding, called by public LoadEvent() methods

 Decodes prescale factors from either
 TS_PRESCALE_EVTYPE(default) = PS factors
 read from Trig. Super. registors (since 11/03)
   - or -
 PRESCALE_EVTYPE = PS factors from traditional
     "prescale.dat" file.

 Decode scalers

 Get scaler data by spectrometer, slot, and channel
 spec = "left" or "right" for the "scaler events" (type 140)
 and spec = "evleft" and "evright" for scalers
 that are part of the event (ev) readout.

 Get scaler data by roc, slot, chan.

 Test if the given EPICS variable name has been loaded

 EPICS data which is nearest CODA event# 'event'
 event == 0 --> get latest data
 Tag is EPICS variable, e.g. 'IPM1H04B.XPOS'

 EPICS string data which is nearest CODA event# 'event'
 event == 0 --> get latest data

 EPICS time stamp
 event == 0 --> get latest data

 Decode VME

 Looks for buffer mode and synch problems.  The latter are recoverable
 but extremely rare, so I haven't bothered to write recovery a code yet,
 but at least this warns you.

 Set run time and re-initialize crate map (and possibly other
 database parameters for the new time.