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Instruction Formats 3–5
3.2.2 Instruction Operand Notation
The notation used to describe instruction operands follows from the operand specifier notation
used in the VAX Architecture Standard. Instruction operands are described as follows:
<name>.<access type><data type>
3.2.2.1 Operand Name Notation
Specifies the instruction field (Ra, Rb, Rc, or disp) and register type of the operand (integer or
floating). It can be one of the following:
3.2.2.2 Operand Access Type Notation
A letter that denotes the operand access type:
Table 3–4: Operand Name Notation
Name Meaning
disp The displacement field of the instruction
fnc The PALcode function field of the instruction
Ra An integer register operand in the Ra field of the instruction
Rb An integer register operand in the Rb field of the instruction
#b An integer literal operand in the Rb field of the instruction
Rc An integer register operand in the Rc field of the instruction
Fa A floating-point register operand in the Ra field of the instruction
Fb A floating-point register operand in the Rb field of the instruction
Fc A floating-point register operand in the Rc field of the instruction
Table 3–5: Operand Access Type Notation
Access Type Meaning
a The operand is used in an address calculation to form an effective
address. The data type code that follows indicates the units of addressabil-
ity (or scale factor) applied to this operand when the instruction is
decoded.
For example:
".al" means scale by 4 (longwords) to get byte units (used in branch dis-
placements); ".ab" means the operand is already in byte units (used in
load/store instructions).
i The operand is an immediate literal in the instruction.