Mitsubishi MELSEC iQ-F FX5 series, Programming Manual, Page: 458 / 888

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7 APPLICATION INSTRUCTION
7.7 Real Number Instruction
Calculating the natural logarithm of single-precision real number
LOG(P)/DLOGE(P)
These instructions calculate the logarithm whose base is natural logarithm e of a value specified by (s), and store the
operation result in the device specified by (d).
The LOG(P) instructions can also be used as DLOGE(P).
*1 The LOG instruction is not supported by the ST language. Use LOG of the standard function.

Page 768 LOG(_E)
Setting data
■
Descriptions, ranges, and data types
■
Applicable devices
Processing details
• These instructions calculate the logarithm whose base is natural logarithm e of a value specified by (s), and store the
operation result in the device specified by (d).
• Only a positive value can be set in (s). (The natural logarithm operation cannot be executed for a negative value).
• The table below shows the related devices.
Ladder diagram Structured text
*1
ENO:=LOGP(EN,s,d);
Operand Description Range Data type Data type (label)
(s) Data whose natural logarithm is calculated or head device
number where the data is stored

Single-precision real number Single-precision real number
(d) Head device number for storing the operation result

Single-precision real number Single-precision real number
Operand Bit Word Double word Indirect
specification Constant Others
X, Y, M, L,
SM, F, B, SB U

\G

T, ST,
C, LC T, ST, C, D,
W, SD, SW, R U

\G

Z LC LZ K, H E $
(s)
            
(d)
            
Device Name Description
Condition Operation
SM700 Carry The absolute value of the operation result

2
128
The value of (d) is the maximum value (2
128
) of 32-bit real
numbers and the carry flag SM700 turns on.
SM8020 Zero The operation result is true "0".
(The mantissa part is "0"). The zero flag SM8020 turns on.
SM8021 Borrow The absolute value of the operation result < 2
-126
The value of (d) is the minimum value (2
-126
) of 32-bit real
numbers and the borrow flag SM8021 turns on.
SM8022 Carry The absolute value of the operation result

2
128
The value of (d) is the maximum value (2
128
) of 32-bit real
numbers and the carry flag SM8022 turns on.
(s) (d)
(s)+1 (s) (d)+1 (d)
log ( )
Single-precision real number Single-precision real number