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CHAPTER2 SEQUENCE PROGRAMS
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2.4 Data Used in Sequence Programs
2.4.4 Real number (Floating-point data)
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(2) Double-precision floating-point data
(a) Internal representation
Real number data used in the CPU module is internally represented as follows, using four word
devices.
[Sign] 1. [Mantissa] 2
[Exponent]
The bit configuration and the meaning of each bit are described below.
1) Sign
The most significant bit, b63, is the sign bit.
0: Positive
1: Negative
2) Exponent
The 11 bits, b52 to b62, represent the excess n of 2
n
.
The following shows the excess n according to the binary values in b52 to b62.
3) Mantissa
Each of the 52 bits, b0 to b51, represents the "XXXXXX..." portion when the data is represented in binary,
"1.XXXXXX...".
Figure 2.40 Bit configuration of real number data
Figure 2.41 Relation between the exponent and excess n
b63 b62
to
b52 b51
to
b16 b15
to
b0
b63
b0 to b51
Mantissa (52 bits)
b52 to b62
Exponent (11 bits)
Sign
b52 to b62
n
7FF
H
7FEH
1023
7FD
H
1022
00
H
Not usedNot used
02H
-1021
01
H
-1022
400
H
2
3FF
H
1
3FE
H
0
3FD
H
-1
3FC
H
-2