Solution:

The main defference is that PCL-812PG's input range selection is by software and PCL-812's is by DIP switch respectively. There are also differences in available input ranges : The input range of PCL-812 are: Bipolar: +/- 1V, +/- 2V, +/- 5V, +/- 10V The input range of PCL-812PG are: Bipolar: +/- 0.3125V, +/- 0.625V, +/- 1.25V, +/- 2.5V, +/- 5V, +/-10V The ADC574.PDF was the data sheet of ADC574 (compatible as HADC574Z) which used by PCL-812, and another one was the upgrade chip of ADC574 which used by PCL-812PG.