Mitsubishi Electronics FX3G User Manual

510

/FX

3GC

/FX

3UC

Series

Programming Manual - Basic & Applied Instruction Edition

18 Floating Point – FNC110 to FNC139

18.12 FNC124 – EXP / Floating Point Exponent

Program example

In the program example shown below, the exponential operation is executed for a value set in the 2-digit BCD format
in X020 to X027, and the operation result is stored in the binary floating point format to D0 and D1 when X000 turns
ON.

Operation when "13" is specified in X020 to X027

Points

1) The operation result becomes less than "2

128

" when the BCD value set in X020 to X027 is "88" or less because of

"loge2

128

= 88.7".

If a value "89" or more is set, an operation error occurs. To prevent this operation error, when a value more than
"89" is set, M0 is set to ON so that the exponential operation is not executed.

2) Conversion from natural logarithm into common logarithm

In the CPU, operations are executed in natural logarithm.
For obtaining a value in common logarithm, specify a common logarithm value divided by "0.4342945" in
[

+1,

X000

FNC224

LD >

D20

Data used in the exponential operation is input ([1]).

The range of the value to be operated is checked.
(Refer to 1) in "Points" below.)

The input data is converted into binary floating point
(real number) ([2]).

The exponential operation is executed ([3]).

K88

FNC 19

BIN

K2X20

D20

FNC 49

FLT

D20

D10

FNC124

DEXP

D10

END

Binary floating point

(real number) value

1 3

[1]

Conversion

into binary

BIN

b15

[2] Conversion into

binary floating point

(real number)

[3]

Exponential

operation

EXP

D11

D10

Binary floating point

(real number) value

442413.4

FLT

D20

X027 X020

BCD value

Binary value

0.4342945