National Instruments Low-Cost Multifunction I/O Board for ISA Lab-PC+ - Manual (Page 133)

Appendix D Register Map and Descriptions
© National Instruments Corporation D-17 Lab-PC+ User Manual
Bit Name Description (continued)
Low Byte
7-0 D<7..0> These bits contain the low byte of the straight binary result of a
12-bit A/D conversion. The first of two consecutive readings of
the A/D FIFO Register always return this byte.
Bit Map: Two's complement binary mode
High Byte
7 6 5 4 3 2 1 0
D15 D14 D13 D12 D11 D10 D9 D8
{ Sign Extension Bits }
Low Byte
7 6 5 4 3 2 1 0
D7 D6 D5 D4 D3 D2 D1 D0
Bit Name Description
High Byte
7-0 D<15..8> These bits contain the high byte of the 16-bit, sign-extended two's
complement result of a 12-bit A/D conversion. Values made up of
D<15..0>, therefore, range from -2,048 to +2,047 decimal (F800 to
07FF hex). Two's complement mode is useful for bipolar analog
input readings because the values read reflect the polarity of the
input signal.
Low Byte
7-0 D<7..0> These bits contain the low byte of the 16-bit, sign-extended two's
complement result of a 12-bit A/D conversion. The first of two
consecutive readings of A/D FIFO Register always returns this
byte.