Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

166

Saturating Double and Add and Saturating Double and Subtract, signed.
Syntax

op{cond} {Rd}, Rm, Rn

where:
opis one of:
QDADD Saturating Double and Add.
QDSUB Saturating Double and Subtract.
condis an optional condition code, see 

.

Rdis the destination register.
Rm, Rnare registers holding the first and second operands.
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.
Examples

QDADD

  R7, R4, R2 

; Doubles and saturates R4 to 32 bits, adds R2,

 ; saturates to 32 bits, writes to R7

QDSUB

   R0, R3, R5

; Subtracts R3 doubled and saturated to 32 bits

 ; from R5, saturates to 32 bits, writes to R0.