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

 141

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

If X is present, the multiplications are bottom × top and top × bottom.
If the X is omitted, the multiplications are bottom × bottom and top × top.

cond

Rd

is the destination register.

Rn, Rm

are registers holding the first and second operands.

Operation

The SMUAD instruction interprets the values from the first and second operands as two signed halfwords in each
operand. This instruction: 



Optionally rotates the halfwords of the second operand.



Performs two signed 16 × 16-bit multiplications.



Adds the two multiplication results together.



Writes the result of the addition to the destination register.

The SMUSD instruction interprets the values from the first and second operands as two’s complement signed integers.
This instruction:



Optionally rotates the halfwords of the second operand.



Performs two signed 16 × 16-bit multiplications.



Subtracts the result of the top halfword multiplication from the result of the bottom halfword multiplication.



Writes the result of the subtraction to the destination register.

Restrictions

In these instructions:



Do not use SP and do not use PC.

Condition Flags

Sets the Q flag if the addition overflows. The multiplications cannot overflow.

Examples

SMUAD

R0, R4, R5

; Multiplies bottom halfword of R4 with the bottom

; halfword of R5, adds multiplication of top halfword

; of R4 with top halfword of R5, writes to R0

SMUADX

R3, R7, R4

; Multiplies bottom halfword of R7 with top halfword

; of R4, adds multiplication of top halfword of R7

; with bottom halfword of R4, writes to R3

SMUSD

R3, R6, R2

; Multiplies bottom halfword of R4 with bottom halfword

; of R6, subtracts multiplication of top halfword of R6

; with top halfword of R3, writes to R3

SMUSDX

R4, R5, R3

; Multiplies bottom halfword of R5 with top halfword of

; R3, subtracts multiplication of top halfword of R5

; with bottom halfword of R3, writes to R4.

Signed Multiply (halfwords) and Signed Multiply (word by halfword)

Syntax

op{XY}{cond} Rd,Rn, Rm

op{Y}{cond} Rd. Rn, Rm

For SMULXY only:

op

is one of:

SMUL{XY}         Signed Multiply (halfwords).

X and Y specify which halfword of the source registers Rn and Rm is used as
the first and second multiply operand.