Automating Manufacturing Systems - Process Control and ...

plc numbers - 13.5
shown in Figure 13.5. Notice that on both numbers the least significant digit is on the right
hand side of the numbers. And, in the word there are two bytes, and the right hand one is
the least significant byte.
BYTE
WORD
MSB
LSB
MSB
LSB
0110 1011
0110 1011 0100 0010
most
significant
byte
least
significant
byte
Figure 13.5
Bytes and Words
Binary numbers can also represent fractions, as shown in Figure 13.6. The conversion
to and from binary is identical to the previous techniques, except that for values to the
right of the decimal the equivalents are fractions.
binary:
101.011
12 ( 2 ) = 4 0( 2 1 ) = 0 1( 2 0 ) = 1 0( 2 – 1 ) = 0 12 ( – 2 )
1
= -- 1( 2 – 3 )
4
=
1
--
8
1
4 0 1 0 --
1
= + + + + + -- = 5.375
4 8
decimal
Figure 13.6
A Binary Decimal Number
13.2.1.1 - Boolean Operations
In the next chapter you will learn that entire blocks of inputs and outputs can be
used as a single binary number (typically a word). Each bit of the number would correspond
to an output or input as shown in Figure 13.7.