Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 150

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

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

Syntax

op{cond} {Rd}, Rm, Rn

where:

op

is one of:

QDADD Saturating Double and Add.

QDSUB Saturating Double and Subtract.

cond

Rd

is the destination register.

Rm, Rn

are 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.