9.2 Analog IO Ranges

Several of the boards support programmable input ranges and resolution. For these boards, a table has been included detailing all possible A/D range settings. Here is a detailed description of the data in the tables:

Code	This is the code for the particular input range
Range	This bit selects the board's A/D positive full-scale voltage range; 0 = 5V, 1 = 10V. Do not confuse this term with the board's "input range."
ADBU	This bit selects the board's A/D bipolar/unipolar setting; 0 = bipolar, 1 = unipolar.
G1, G0	These bits select the board's A/D gain setting. The gain settings and their respective control bits are as follows: G1 G0 Gain 0 0 1 0 1 2 1 0 4 1 1 8
Input Range	This column lists the input range resulting from the particular configuration of control bits.
Resolution	This column lists the voltage resolution resulting from the particular configuration of control bits. The resolution is equal to the smallest change in input voltage detectable by the A/D circuit. This smallest change results in a change in A/D code of 1 least significant bit, or LSB. The resolution is equal to the total voltage range (maximum input voltage - minimum input voltage) divided by the number of possible A/D codes (2n where n is the number of bits in the A/D converter). For an input range of ±5V and a 16-bit A/D converter, the resolution is (+5V - -5V) / 216 = 10 / 65536 = .000153V or 153μV.