Mitsubishi Electric MELSEC-Q00U(J)CPU User Manual page 541

(b) Replacing a part of floating-point operation instructions with double-precision
floating-point operation instructions
Only operations that require high accuracy are replaced with double-precision floating-point operation
instructions.
Using the ECON and EDCON instructions, convert floating-point data mutually between single precision and
double-precision. The flow of a replacement program is as follows:
• Data required for operations are converted from single precision to double precision using the ECON
instruction.
• Operations are performed in double precision using the double-precision floating-point operation
instructions.
• Operation results are converted from double precision to single precision using the EDCON instruction.
A program example that floating-point data are converted mutually between single precision and double
precision before and after operations is shown below.
Replacing the floating-point operation [A × B + C] (Using the ECON and EDCON instructions)
Ex.
• Device assignment
Before replacement
Application Device
Data A D0 to D1
Data B D2 to D3
Data C D4 to D5
Result D6 to D7
• Program before replacement
• Program after replacement
Data type Application
Data A
Data B
Floating-point data
(single precision)
Data C
Result
Data A
Data B
Data C
Result
APPENDICES
After replacement
Device Data type
D0 to D1
D2 to D3
Floating-point data
(single precision)
D4 to D5
D6 to D7
D10 to D13
D14 to D17
Floating-point data
(double precision)
D18 to D21
D22 to D25
Floating-point data are
converted from single precision
to double precision.
Operation is performed using
double-precision floating-point
data.
The floating-point operation result
data are converted from double
precision to singe precision.
A
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