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126
11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
11.6.5.17
UASX and USAX
Add and Subtract with Exchange and Subtract and Add with Exchange.
Syntax
op{cond} {Rd}, Rn, Rm
where:
Operation
The
UASX
instruction:
1.
Subtracts the top halfword of the second operand from the bottom halfword of the first
operand.
2.
Writes the unsigned result from the subtraction to the bottom halfword of the destina-
tion register.
3.
Adds the top halfword of the first operand with the bottom halfword of the second
operand.
4.
Writes the unsigned result of the addition to the top halfword of the destination register.
The
USAX
instruction:
1.
Adds the bottom halfword of the first operand with the top halfword of the second
operand.
2.
Writes the unsigned result of the addition to the bottom halfword of the destination
register.
3.
Subtracts the bottom halfword of the second operand from the top halfword of the first
operand.
4.
Writes the unsigned result from the subtraction to the top halfword of the destination
register.
Restrictions
Do not use SP and do not use PC
.
Condition Flags
These instructions do not affect the condition code flags.
Examples
UASX
R0, R4, R5
; Adds top halfword of R4 to bottom halfword of R5 and
; writes to top halfword of R0
; Subtracts bottom halfword of R5 from top halfword of R0
; and writes to bottom halfword of R0
USAX
R7, R3, R2
; Subtracts top halfword of R2 from bottom halfword of R3
; and writes to bottom halfword of R7
; Adds top halfword of R3 to bottom halfword of R2 and
; writes to top halfword of R7.
op
is one of:
UASX
Add and Subtract with Exchange.
USAX
Subtract and Add with Exchange.
cond
is an optional condition code, see
Rd
is the destination register.
Rn, Rm
are registers holding the first and second operands.
Содержание SAM4S Series
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