Mitsubishi Electric Q01UCPU User Manual page 532

(3) Advantages and disadvantages when using the double-precision floating-point
data of the Universal model QCPU
The following table shows the advantages and disadvantages when executing the double-precision floating-point
operation instructions in the Universal model QCPU.
If higher accuracy is required in floating-point operations, it is recommended to replace the instructions with the
double-precision floating-point operation instructions.
The results are more accurate than those of the
single-precision floating-point operation
instructions.
*1 The processing speed of the double-precision floating-point operation instructions in the Universal model QCPU is
higher than that of floating-point operation instructions using internal double-precision operations in the High
Performance model QCPU.
The following table lists the comparison between single-precision and double precision floating-point data.
Item
Word point required for data retention
Setting range
Precision (number of bits)
Instruction processing
speed (Q04UDHCPU/
Q06UDHCPU) (minimum)
Instruction processing
speed (High-speed
Universal model QCPU)
(minimum)
530
Advantage
Mantissa
Exponent
Sign
Data comparison (Conductive
status) (LDE>= / LDED>=)
Data transfer
(EMOV/EDMOV)
Addition (3 devices)
(E+ / ED+)
SIN operation (SIN/SIND)
Data comparison (Conductive
status) (LDE>= / LDED>=)
Data transfer
(EMOV/EDMOV)
Addition (3 devices)
(E+ / ED+)
SIN operation (SIN/SIND)
Disadvantage
The instruction processing speed is slower than that of the single-
precision floating-point operation instructions.
Double-precision floating-operation data use twice as many word device
points as single-precision floating-operation data.
Single-precision
floating-point data
2 words
128 -126
< N -2
-2 , 0,
-126 128
N < 2
2
23
bits
8
bits
1
bit
0.0285
µs
0.019
µs
0.0665
µs
4.1
µs
0.0098
µs
0.0039
µs
0.015
µs
1.6
µs
*1
Double-precision
floating-point data
4 words
1024 -1022
<N -2
-2 , 0,
-1022 1024
N < 2
2
52
bits
11
bits
1
bit
3.6
µs
1.7
µs
4.8
µs
8.5
µs
1.8
µs
0.0078
µs
1.9
µs
2.6
µs