Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO データシート

SAM4E [DATASHEET]

Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14

160

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

is an optional condition code, see 

.

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.