Rockwell Automation 1746-NI8 SLC 500 Analog Input Modules User Manual - Manual (Page 83)

Variable Content TTL:Chap D–2
Publication 1746Ć6.8 - April 1997
Negative Decimal Values
In two’s complement notation, the far left position is always 1 for
negative values. The equivalent decimal value of the binary number
is obtained by subtracting the value of the far left position, 32768,
from the sum of the values of the other positions. In the figure
below (all positions are 1), the value is 32767 – 32768 = –1. For
example:
1111 1000 0010 0011 =
(2 14 +2 13 +2 12 +2 11 +2 5 +2 1 +2 0 ) - 2 15 =
(16384+8192+4096+2048+32+2+1) - 32768 =
30755 - 32768 = -2013.
1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1x2 14 = 16384
1 x 2 15 = 1 This position is always 1 for negative numbers
1x 2 13 = 8192
1x 2 12 = 4096
1x 2 11 = 2048
1x 2 10 = 1024
1x 2 9 = 512
1x 2 8 = 256
1x 2 7 = 128
1x 2 6 = 64
1x 2 5 = 32
1x 2 4 = 16
1x 2 3 = 8
1x 2 2 = 4
1x 2 1 = 2
1x 2 0 = 1
16384
8192
4096
2048
1024
512
256
128
64
32
16
8
4
2
1
32767