Xilinx Virtex-II Pro PPC405, User Manual

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March 2002 Release www.xilinx.com 313
Virtex-II Pro™ Platform FPGA Documentation 1-800-255-7778
Document Conventions
R
Instruction Fields
Table 2 lists the instruction fields used in the various instruction formats. They are found in
the instruction encodings and pseudocode, and are referred to throughout this document
when describing instructions. The table includes the bit locations for the field within the
instruction encoding.
cr_field Used in simplified mnemonics to specify a CR field
(0 to 7) used as an operand.
OBJECT
b
A single bit in any object (a register, an instruction, an
address, or a field) is shown as a subscripted number or
name.
OBJECT
b:b
A range of bits in any object (a register, an instruction,
an address, or a field).
OBJECT
b,b, . . .
A list of bits in any object (a register, an instruction, an
address, or a field).
REGISTER[FIELD] Fields within any register are shown in square brackets.
REGISTER[FIELD, FIELD
. . .
] A list of fields in any register.
REGISTER[FIELD:FIELD] A range of fields in any register.
Table P-1: General Notational Conventions (Continued)
Convention Definition
Table P-2: Instruction Field Definitions
Field Location Description
AA 30 Absolute-address bit (branch instructions).
0—The immediate field represents an address relative to the
current instruction address (CIA). The effective address (EA) of
the branch is either the sum of the LI field sign-extended to 32
bits and the branch instruction address, or the sum of the BD
field sign-extended to 32 bits and the branch instruction address.
1—The immediate field represents an absolute address. The EA of
the branch is either the LI field or the BD field, sign-extended to
32 bits.
BD 16:29 An immediate field specifying a 14-bit signed two’s-complement
branch displacement. This field is concatenated on the right with
0b00 and sign-extended to 32 bits.
BI 11:15 Specifies a bit in the CR used as a source for the condition of a
conditional-branch instruction.
BO 6:10 Specifies options for conditional-branch instructions. See
Conditional Branch Control , page 367
crb A 11:15 Specifies a bit in the CR used as a source of a CR-logical instruction.
crb B 16:20 Specifies a bit in the CR used as a source of a CR-logical instruction.
crb D 6:10 Specifies a bit in the CR used as a destination of a CR-Logical
instruction.