DFEC -- DFE Crate Controller
Original Version 

Originally designed for a PIC microcontroller, this was
actually implemented and some basic CompactFlash file
system routines were coded up by Nick Weydert (summer
student) in assembly.  Then we realized that the little
PIC sucked, so a small adapter board was designed to replace
the PIC with an ATMEL AVR RISC microcontroller.

This new micro supported the FAT16 file system, very useful since now the
CompactFlash card could be removed and read by a notebook PC during an
access!  All code written in C--

FPGA implements the backplane interface and 1553 RT logic as well a dual
port ram where data is transferred to and from the micro.

One board mod... the 12MHz clock is connected directly to the BPCLK buffer
input, so that trace coming to from the FPGA must be cut.


                    Notice! Attenzione! Achtung!


The MIXER crate uses an older version of the DFEC FPGA code (v2.20)  due
to the way the "slow monitor" status bits are collected from the Mixer
boards.  Installing a newer firmware version in the DFEC will still work
for backplane reads and writes, and file initialization, but the status
bits will be wrong.  The newer DFEC firmware is trying to collect 192 bits
per board and put it in the MBSTAT area -- the mixer boards do not support
this.

JTO 30 March 2006