Mitsubishi Electric MELSEC-Q00U(J)CPU

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APPENDICES
A
Appendix 5 Replacing Basic Model QCPU or Qn(H)CPU with QnUCPU Appendix 5.4 Functions
(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.
*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.
Advantage Disadvantage
The results are more accurate than those of the
single-precision floating-point operation
instructions.
The instruction processing speed is slower than that of the single-
precision floating-point operation instructions.
*1
Double-precision floating-operation data use twice as many word device
points as single-precision floating-operation data.
Item
Single-precision
floating-point data
Double-precision
floating-point data
Word point required for data retention 2 words 4 words
Setting range
-2
128
< N -2
-126
, 0,
2
-126
N < 2
128
-2
1024
<N -2
-1022
, 0,
2
-1022
N < 2
1024
Precision (number of bits)
Mantissa 23 bits 52 bits
Exponent 8 bits 11 bits
Sign 1 bit 1 bit
Instruction processing
speed (Q04UDHCPU/
Q06UDHCPU) (minimum)
Data comparison (Conductive
status) (LDE>= / LDED>=)
0.0285µs 3.6µs
Data transfer
(EMOV/EDMOV)
0.019µs 1.7µs
Addition (3 devices)
(E+ / ED+)
0.0665µs 4.8µs
SIN operation (SIN/SIND) 4.1µs 8.5µs
Instruction processing
speed (High-speed
Universal model QCPU)
(minimum)
Data comparison (Conductive
status) (LDE>= / LDED>=)
0.0098µs 1.8µs
Data transfer
(EMOV/EDMOV)
0.0039µs 0.0078µs
Addition (3 devices)
(E+ / ED+)
0.015µs 1.9µs
SIN operation (SIN/SIND) 1.6µs 2.6µs