Filter
Top Products
4–116 Alpha Architecture Handbook
4.10.11 Convert VAX Floating to VAX Floating
Format:
Operation:
Fc ← {conversion of Fbv}
Exceptions:
Instruction mnemonics:
Qualifiers:
Description:
The floating operand in register Fb is converted to the specified alternate floating format and
written to register Fc. Register Fa must be F31.
An invalid operation trap is signaled if the operand has exp=0 and is not a true zero (that is,
VAX reserved operands and dirty zeros trap). The contents of Fc are UNPREDICTABLE if
this occurs.
See Section 4.7.7 for details of the stored result on overflow or underflow.
Notes:
• The only arithmetic operations on D_floating values are conversions to and from
G_floating. The conversion to G_floating rounds or chops as specified, removing three
fraction bits. The conversion from G_floating to D_floating adds three low-order zeros
as fraction bits, then the 8-bit exponent range is checked for overflow/underflow.
• The conversion from G_floating to F_floating rounds or chops to single precision, then
the 8-bit exponent range is checked for overflow/underflow.
• No conversion from F_floating to G_floating is required, since F_floating values are
always stored in registers as equivalent G_floating values.
CVTxy Fb.rx,Fc.wx
!Floating-point Operate format
Invalid Operation
Overflow
Underflow
CVTDG Convert D_floating to G_floating
CVTGD Convert G_floating to D_floating
CVTGF Convert G_floating to F_floating
Rounding: Chopped (/C)
Trapping: Exception Completion (/S)
Underflow Enable (/U)