Mitsubishi Electric MELSEC-Q00U(J)CPU User Manual page 501

(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
The bit configuration and the meaning of each bit are described below.
b63 b62
to
b63
b52 to b62
Exponent (11 bits)
Sign
• Sign
The most significant bit, b63, is the sign bit.
0: Positive
1: Negative
• Exponent
The 11 bits, b52 to b62, represent the excess n of 2
The following shows the excess n according to the binary values in b52 to b62.
b52 to b62 7FF 7FE
H
n
Not used 1023
• Mantissa
Each of the 52 bits, b0 to b51, represents the "XXXXXX..." portion when the data is represented in binary,
"1.XXXXXX...".
[Exponent]
b52 b51 b16 b15
to
7FD 400 3FF
H H H H
1022 1 0
to
b0 to b51
Mantissa (52 bits)
n
.
3FE 3FD 3FC
H H H
-1 -2 -3 -1021
APPENDICES
b0
02 01 00
H H H
-1022 Not used
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