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March 2002 Release
821
Virtex-II Pro™ Platform FPGA Documentation
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R
Appendix C
Simplified Mnemonics
Simplified mnemonics (sometimes referred to as extended mnemonics) define a shorthand
used by assemblers for the most-frequently used forms of several instructions.
Branch Instructions
Two classes of simplified branch mnemonics are provided.
summarizes the simplified branch-conditional mnemonics that test if a condition is true or
false. The condition tested can include a specific bit (
b
) in the CR, whether or not the
contents of the CTR are zero, or both.
summarizes the simplified
branch-conditional mnemonics that test a comparison condition. Instructions in that table
specify a CR
n
field (
n
) that is checked for a particular comparison result.
True/False Conditional Branches
True/false conditional branches test a condition and branch if the condition is met. The
condition tested can include a specific bit (
b
) in the CR, whether or not the contents of the
CTR are zero, or both. The simplified mnemonics in
through
are
formed using the following syntax (angle brackets denote an optional field):
b<CTR decrement><CTR test><CR test><LR target><CTR target><LR update><absolute target>
shows the abbreviations used in the formation of the simplified branch
mnemonics.
The detailed instruction syntax for the simplified mnemonics listed in
are shown
. A cross-reference to the appropriate table is shown in the
column heading of
Table C-1:
Abbreviations for True/False Conditional Branches
Abbreviation
Description
Mnemonic Field
d
Decrement CTR
CTR decrement
nz
Branch if CTR
≠
0
CTR test
z
Branch if CTR
=
0
CTR test
f
Branch if condition false (CR
b
=
0)
CR test
t
Branch if condition true (CR
b
=
1)
CR test
lr
Branch to target address in LR
LR target
ctr
Branch to target address in CTR
CTR target
l
Update LR with return address (LK opcode field
=
1)
LR update
a
Branch to absolute address (AA opcode field
=
1)
absolute target
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