ComputerVoltageSources

"Grant Richter" <grichter@...> wrote:
>
> >   
> > * 4-channels serially loaded DAC.
> >   What brand of DAC was used on the PSIM?
> >   2 Dual DACs or one Quad DAC?
> >   Separate or simultaneous load strobe?
> >   How many bits?
> 
> Lack of port pins keeps it to a serial interface. The AD8420 is the
original to the DAC7714 
> and requires no software change. The DAC7714 is only available in
surface mount where 
> the DAC8420 is available in DIP or SM. The DAC8420 is $44 single
piece. Probably put a 
> dual footprint on the board for DIP or SM.
> 
> http://www.analog.com/en/prod/0%2C2877%2CDAC8420%2C00.html
> 
> All 4 input channels can be read and all 4 output channels updated
in 1.2 millisecond. 
> Plenty fast for CV generation.

I want to bring up an issue that was uncovered in early PSIM usage -
although the DAC outputs were precise enough for 1 v/oct scaling, the
INPUTS were not as precise - for instance, when using Woody Wall's
Quantized Shift Register, errors were discovered when sampling a
pre-quantized source (the shift register's output was a different
pitch than the input).  When discussing this with Grant, he surmised
that it was the lack of bit resolution on the input side, which had a
limited precision - therefore the encoding error.  Can we address this
hardware issue?

Conxiser this please, oh kind sirs, (bowing as I recceed back into the
shaddows) 8-)

gary