Signed-magnitude binary two's complement binary – Rockwell Automation 1771-IXE/D Thermocouple/Millivolt Input Module User Manual User Manual
Page 64
Data Table Formats
C–2
Publication 1771-6.5.130 Ć May 1999
Table C.A BCD Representation
Place Value
2
3
(8)
2
2
(4)
2
1
(2)
2
0
(1)
Decimal
Equivalent
0
0
0
0
0
0
0
0
1
1
0
0
1
0
2
0
0
1
1
3
0
1
0
0
4
0
1
0
1
5
0
1
1
0
6
0
1
1
1
7
1
0
0
0
8
1
0
0
1
9
Signed–magnitude binary is a means of communicating numbers to
your processsor. It should be used with the PLC–2 family when
performing computations in the processor. It cannot be used to
manipulate binary 12–bit values or negative values.
Example: The following binary number is equal to decimal 22.
10110
2
= 22
10
The signed–magnitude method places an extra bit (sign bit) in the
left–most position and lets this bit determine whether the number is
positive or negative. The number is positive if the sign bit is 0 and
negative if the sign bit is 1. Using the signed magnitude method:
0 10110 = +22
1 10110 = –22
Two’s complement binary is used with PLC–3 processors when
performing mathematical calculations internal to the processor. To
complement a number means to change it to a negative number. For
example, the following binary number is equal to decimal 22.
10110
2
= 22
10
Signed-magnitude Binary
Two's Complement Binary