DC Electronics:  Design Changes since the PDR

1) Amplifier IC (DCAC)

   Some functionality not used in the BABAR implementation
has been removed (specifically the analog output gain adjust
and the analog output drivers).

2) ELEFANT IC

  The prototype had problems in the analog receiver that were
corrected by a revised design.  The pre-production version
was fully functional.  Some changes went into the production
version to stop coupling of noise from the FADC comparators
to the analog receiver and out the TDC inputs.

3)  Amplifier-Digitizer Board (ADB)

  No significant changes to the ADB design.  Principal changes have 
been to accommodate changes in the DCAC and ELEFANT chips.

4)  Readout Interface Board (RIB)

  Several changes were made to the sub-system Fast Control commands
to provide more flexibility and diagnostics.  One command was added
to turn off individual ELEFANT chips in the readout.  Another 
register bit was added to force readout of all channels of all
elefants (i.e. override the sparsing feature).
  The handling of trigger data coming from the ADB has been 
finalized.  Some re-arrangement of the serialization circuitry
was done to meet the requirements of the DC trigger system.
  The previous design had power regulators on a separate board. This
board is gone and the regulators are now on the RIB.

5)  Data I/O Module

  There was not a full schematic of the Data and Trigger I/O module at 
the time of the PDR.  Schematics exist for both now.  A prototype of the 
DIOM exists and is being tested.  Revised reliability numbers allowed
us to remove the redundant links in this and the Trigger I/O module.
TTL drivers are used, which has eliminated the need for a -8 volt 
supply.
  The environmental monitoring controller was moved onto the DIOM board
with one controller covering each quadrant.

6)  Trigger I/O Module

  Schematics exist for the Trigger I/O module and the board layout is
nearing completion.  The interface with the trigger system has been 
finalized.  Synchronization is established and maintained by sending a
control word at the beginning of each frame of serial data.
  As in the DIOM, TTL drivers are used, eliminating the need for -8 volts.
  G-links are monitored by a micro-controller that reports a status bit
back to the Data I/O module.

7)  Environmental Monitoring

  As mentioned above, the controller was moved into the Data I/O Module (many
of the sensors are temperature and voltage sensors whose signals are included in
the FEA-DIOM cable).