Natural Logarithm

Instruction Parameters

Supported PLC Series

XPnA/1R	XPnB	XPnE	XPnF	CP3A/B/P/U CP4A~D/U	CPnE	CPnF	BP	PLC-S
✓	✓	✓	✓	-	-	-	-	✓

Supported Data Registers

	M	X	Y	K	L	F	T	C	S	Z	R	Q	D	@D	Constant
S	✓	✓	✓	✓	✓	-	-	-	-	✓	-	✓	✓	✓	✓
D	✓	-	✓	✓	✓	-	-	-	-	✓	-	✓	✓	✓	-

Supported Flags

Flag	Bit	Support
Error	F11.0	✓
Zero	F11.1	-
Carry	F11.2	-

Number of Steps

Steps
3

Operands

Operand	Description
S	The first operand. Entries are REAL data registers or constants. This is the value to calculate the natural log of. The value range is 1 ~ 2128 (1 ~ 3.4028237e+38).
D	The second operand. Entries are only REAL data registers. This is where the logarithm is saved.

Float Representation

Mantissa	Exponent	Sign
Bit 0 ~ Bit 22	Bit 23 ~ Bit 30	Bit 31

Notice

Error Flag (F11.0) Notice

The error flag, F11.0, will be ON for one scan when the address of the data register assigned by @D exceeds the range of the data register, D. The range of the data register, D, is dependent on the CPU type.

F11.0 turns ON when the value of S is negative or 0.

Instruction Behavior

The LOG and LOGP instructions behave as follows:

• The natural logarithm executes using base e.
  • Execution is done ln(S).
  • The PLC CPU regards the constant e as 2.71828.

Examples

• Ladder Diagram