x86 Instruction Set Reference

FBLD

Load Binary Coded Decimal

Opcode Mnemonic Description
DF /4 FBLD m80 dec Convert BCD value to floating-point and push onto the FPU stack.
Description

Converts the BCD source operand into double extended-precision floating-point format and pushes the value onto the FPU stack. The source operand is loaded without rounding errors. The sign of the source operand is preserved, including that of -0.

The packed BCD digits are assumed to be in the range 0 through 9; the instruction does not check for invalid digits (AH through FH). Attempting to load an invalid encoding produces an undefined result.
Operation 
TOP = TOP - 1;
ST(0) = ConvertToExtendedDouble(Source);
FPU flags affected

C1 Set to 1 if stack overflow occurred; otherwise, set to 0. C0, C2, C3 Undefined.

Floating-Point Exceptions
#ISStack overflow occurred.
Protected Mode Exceptions
#GP(0)If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register contains a null segment selector.
#GP(0)If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register contains a null segment selector.
#SS(0)If a memory operand effective address is outside the SS segment limit.
#NMEM or TS in CR0 is set.
#PF(fault-code)If a page fault occurs.
Real-Address Mode Exceptions
#GPIf a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#GPIf a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#SSIf a memory operand effective address is outside the SS segment limit.
Virtual-8086 Mode Exceptions
#GP(0)If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#GP(0)If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#SS(0)If a memory operand effective address is outside the SS segment limit.
#NMEM or TS in CR0 is set.
#PF(fault-code)If a page fault occurs.