4
FLOG2
Log2
FLOG2
Operation:
Log2 of Source $ FPn
Assembler
FLOG2.<fmt> <ea>,FPn
Syntax:
FLOG2.X FPm,FPn
FLOG2.X FPn
Attributes: Format= (Byte, Word, Long, Single, Double, Extended, Packed)
Description:
Converts the source operand to extended precision (if necessary) and cal-
culates the logarithm of that number using base two arithmetic. Stores the result in
the destination floating-point data register. This function is not defined for input values
less than zero.
Operation Table:
Source In
Range
Destinetion
~ +
Result Log2 NAN 1
Zero
+
-
i nf2
Infinity
+
+inf NAN 1
NOTES:
1. Sets the OPERR bit in the FPSR exception byte.
2, Sets the DZ bit in the FPSR exception byte.
3. If the source operand is a NAN, refer to 4.5.4 NANs for more information.
Status Register:
Condition Codes:
Quotient Byte:
Exception Byte:
Accrued Exception Byte:
Affected as described in 4.5.5.1 SETTING FLOATING-POINT
CONDITION
CODES
Not affected
BSUN
SNAN
OPERR
OVFL
UNFL
DZ
Cleared
Refer to 4.5.4
NANs.
Set if the source is < 0; cleared otherwise
Cleared
Cleared
Set if the source is (+ or -)0; cleared other-
wise
INEX2 Refer to 6.1.7 Inexact Result.
INEX1 If <fmt> is Packed, refer to 6.1.8 Inexact Result
on
Decimal Input; cleared otherwise.
Affected as described in 6.1.10 IEEE Exception and Trap Com-
patibility
Instruction
Format:
15 14 13 12 11 10 9 8 7 6 5 4 3 2 I 0
• JJCOPROCESSoRFF EFFECTIVEADDRESS
1 I I 1 ID 0 0 0 MODE REGISTER
SOURCE DESTINATION I I I
0 R/M 0 SPECIFIER REGISTER 0 0 I 0 1 1
FREESCALE
4-56
MC68881/MC68882 USER'S MANUAL
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