Atmel SAM4S Series, Preliminary Data Sheet

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155
11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
Examples
QASX R7, R4, R2 ; Adds top halfword of R4 to bottom halfword of R2,
; saturates to 16 bits, writes to top halfword of R7
; Subtracts top highword of R2 from bottom halfword of
; R4, saturates to 16 bits and writes to bottom halfword
; of R7
QSAX R0, R3, R5 ; Subtracts bottom halfword of R5 from top halfword of
; R3, saturates to 16 bits, writes to top halfword of R0
; Adds bottom halfword of R3 to top halfword of R5,
; saturates to 16 bits, writes to bottom halfword of R0.
11.6.7.5 QDADD and QDSUB
Saturating Double and Add and Saturating Double and Subtract, signed.
Syntax
op{cond} {Rd}, Rm, Rn
where:
Operation
The
QDADD
instruction:
• Doubles the second operand value.
• Adds the result of the doubling to the signed saturated value in the first operand.
• Writes the result to the destination register.
The
QDSUB
instruction:
• Doubles the second operand value.
• Subtracts the doubled value from the signed saturated value in the first operand.
• Writes the result to the destination register.
Both the doubling and the addition or subtraction have their results saturated to the 32-bit signed
integer range –2
31
≤ x ≤ 2
31
– 1. If saturation occurs in either operation, it sets the Q flag in the
APSR.
Restrictions
Do not use SP and do not use PC
.
Condition Flags
If saturation occurs, these instructions set the Q flag to 1.
op is one of:
QDADD Saturating Double and Add.
QDSUB
Saturating Double and Subtract.
cond is an optional condition code, see “Conditional Execution” .
Rd is the destination register.
Rm, Rn are registers holding the first and second operands.