Functionality
=============
 o Global: Reload firmware (except for VME!)
           Read R/O data (firmware id, etc)
           Clock select
           Read event data
 o BE:     Soft reset
           Read R/O data (firmware id, etc)
           Read monitor data (temperatures, etc)
           Clear data (QDRs and any internally stored data)
           Select active FEs (mask out FEs with no cable)
           Load configuration data
           Read QDR status and number of events
           Select BE as trigger BE
           Clear trigger
           Load trigger configuration data
           Read trigger status
 o FE:     Soft reset
           Read R/O data (firmware id, VFE types, etc)
           Read monitor data (temperatures, etc)
           Select configuration/run mode (prevent configuration updates or not)
           Load fake event
           Select data/calibration mode (whether to use DACs or not)
           Select no/internal loopback (DAC directly into ADC or not)
           Set DAC value
           Set VFE calibration group
           Select VFE module type (full, right-half or left-half)
           Load timing configuration data


Implementation
==============
Direct VME commands

VME        Clock select
           Board reset
           Reload firmware (except for VME!)
           Vlink read
           Clock counters
           VME firmware id
           Board id and serial number
           VME status


Serial I/O commands, all 32 bit multiples, all MSB first.

BE         D00 - Hard reset
           D01 - Soft reset
           D02 - Firmware id
           D03 - LM82 control
           D04 - LM82 status
           D05 - Config R/W data 
           D06 - Config R/O data
           D07 - Number of events in QDR
           D08 - QDR status
           D09 - Flush all data
           D10 - Software trigger (to single CERC)

           D16 - Set as BE-trigger board
           D17 - Soft reset
           D18 - Config R/W data 
           D19 - Config R/O data
           D21 - Trigger/spill status
           D22 - Trigger reset
           D23 - Flush all data
           D24 - Software trigger (to whole system)

FE         D00 - Hard reset
           D01 - Soft reset
           D02 - Firmware id
           D03 - LM82 control
           D04 - LM82 status
           D05 - Config R/W data 
           D06 - Config R/O data
           D07 - Load fake event
           D08 - Run/config mode change
           D09 - Software trigger (to single FE)