Vfb DAC for TGV's
In each case, I have checked that the TGV32/discriminator responds to the
correct set of serial string bits. I have found an overall offset of
one bit which occurs between the heap manager and the TGV serial
string bits. It appears that the heap manager only captures 15
bits instead of the 16 bits it should take out of the input string.
I do not fully understand the origin of this offset,
but all of the tests below are with this offset included.
If everything works with the exception of this one bit offset,
I have marked that set of bits as "working".
Only 6 of the 8 TGV32 positions on the PC/MCM board
have a chip installed.
This can be monitored at
pad 100, pin 82 -- the pin called disc_vmid on the schematic, not
the pin labeled DAC_VMID on the schematic.
The DAC is reasonably
linear, but has a slightly different slope than the expected values.
This DAC is more or less consistent with numbers shown in
the only documentation of
this DAC's performance I found. Those points are shown as squares
on this plot.
This can be monitored at pad 104, pin 86
on the TGV.
Here is a plot of the DAC output voltage vs. the dac setting:
This plot is also available in postscript.
The data points plotted are available here.
Vfb on TGV 2
this has not been tested yet.
Vfb on TGV 3
this has not been tested yet.
Vfb on TGV 4
this has not been tested yet.
Vfb on TGV 5
this has not been tested yet.
Vfb on TGV 6
this has not been tested yet.
John Sullivan
updated 2-Mar-1999
