Abstract :
~~~~~~~~~
8 bit digital analog converter

Inputs/Outputs :
~~~~~~~~~~~~~~
vd0..vd7  : data inputs
vout      : analog output

Parameters :
~~~~~~~~~~~
vref      : reference voltage that conversion is with respect to 1V
vtrans    : transition voltage between logic high and low        2.5V
tdel      : delay time                                           0s
trise     : rise time                                            0s
tfall     : fall time                                            0s
