Compaq ECQD2KCTE manual Longword Integer Format in Floating-Point Unit, Xfloating Big-Endian Datum

Figure 2–17: X_floating Big-Endian Datum

Byte

0

A:

A+8:

S

Exponent Fraction_high

Byte

15

Fraction_low

Figure 2–18: X_floating Big-Endian Register Format

Byte

0

S Exponent Fraction_high

Fn OR 1

Byte

15

Fraction_low

Fn

2.2.7 Longword Integer Format in Floating-Point Unit

A longword integer operand occupies 32 bits in memory, arranged as shown in Figure 2–19.

Figure 2–19: Longword Integer Datum

31 30	0
S	Integer

:A

A longword integer operand occupies 64 bits in a floating register, arranged as shown in Fig- ure 2–20.

Figure 2–20: Longword Integer Floating-Register Format

63 62 61 59 58 29 28 0

S I xxx

Integer

0

:Fx

There is no explicit longword load or store instruction; the S_floating load/store instructions are used to move longword data into or out of the floating registers. The register bits <61:59> are set by the S_floating load exponent mapping. They are ignored by S_floating store. They are also ignored in operands of a longword integer operate instruction, and they are set to 000 in the result of a longword operate instruction.

The register format bit <62> "I" in Figure 2–20is part of the Integer field in Figure 2–19and represents the high-order bit of that field.

Basic Architecture 2–11