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(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 opera-
tion instructions.
Using the ECON and EDCON instructions, convert floating-point data mutually between single pre-
cision 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 instruc-
tions.
• 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.
1) Device assignment
2) Program before replacement
Example
Replacing the floating-point operation [A B+C] (Using the ECON and EDCON
instructions)
TableApp.37 Device assignment
Before replacement After replacement
Application Device Data type Application Device Data type
Data A D0 to D1
Floating-point data
(single precision)
Data A D0 to D1
Floating-point data
(single precision)
Data B D2 to D3 Data B D2 to D3
Data C D4 to D5 Data C D4 to D5
Result D6 to D7 Result D6 to D7
Data A D10 to D13
Floating-point data
(double precision)
Data B D14 to D17
Data C D18 to D21
Result D22 to D25
Figure App.22 Sample program