Rockwell Automation 1771-IL/B , D17716.5.91 ISOLATED ANALOG INPUT Module - Manual (Page 56)

Data Formats
Appendix C
C-2
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