Negative decimal values – Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual User Manual
Page 98
Publication 1746-UM005B-EN-P - June 2004
B-2 Two’s Complement Binary Numbers
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 on the next
page (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
0x2
15
=
0
This position is always zero for positive numbers
1x2
13
=
8192
1x2
12
=
4096
1x2
11
=
2048
1x2
10
=
1024
1x2
9
=
512
1x2
8
=
256
1x2
7
=
128
1x2
6
=
64
1x2
5
=
32
1x2
4
=
16
1x2
3
=
8
1x2
2
=
4
1x2
1
=
2
1x2
0
=
1
16384
8192
4096
2048
1024
512
256
128
64
32
16
8
4
2
1
32767