Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1407

FBSTP—Store BCD Integer and Pop
Opcode
DF /6
Description
Converts the value in the ST(0) register to an 18-digit packed BCD integer, stores the
result in the destination operand, and pops the register stack. If the source value is a
non-integral value, it is rounded to an integer value, according to rounding mode
specified by the RC field of the FPU control word. To pop the register stack, the
processor marks the ST(0) register as empty and increments the stack pointer (TOP) by
1.
The destination operand specifies the address where the first byte destination value is
to be stored. The BCD value (including its sign bit) requires 10 bytes of space in
memory.
The following table shows the results obtained when storing various classes of numbers
in packed BCD format.
Notes:
Fmeans finite-real number.
Dmeans packed-BCD number.
*indicates floating-point invalid-operation (#IA) exception.
**  0 or  1, depending on the rounding mode.
If the source value is too large for the destination format and the invalid-operation
exception is not masked, an invalid-operation exception is generated and no value is
stored in the destination operand. If the invalid-operation exception is masked, the
packed BCD indefinite value is stored in memory.
If the source value is a quiet NaN, an invalid-operation exception is generated. Quiet
NaNs do not normally cause this exception to be generated.
Operation
DEST  BCD(ST(0));
PopRegisterStack;
Volume 4: Base IA-32 Instruction Reference
Instruction
FBSTP m80bcd
ST(0)
 •
 F <  1
 1 <  F <  0
 0
 0
+0 < +F < +1
+F > +1
+ 
NaN
Description
Store ST(0) in m80bcd and pop ST(0).
DEST
*
 D
**
 0
+0
**
+D
*
*
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