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 135

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

Signed Multiply Accumulate Long Dual

Syntax

op{X}{cond} Rd, Rn, Rm, Ra  ; 

where:

op

is one of:

SMLAD Signed Multiply Accumulate Dual.

SMLADX Signed Multiply Accumulate Dual Reverse.

X specifies which halfword of the source register Rn is used as the multiply
operand.
If X is omitted, the multiplications are bottom × bottom and top × top. 
If X is present, the multiplications are bottom × top and top × bottom.

cond

Rd

is the destination register.

Rn

is the first operand register holding the values to be multiplied.

Rm

the second operand register.

Ra

is the accumulate value.

Operation

The SMLAD and SMLADX instructions regard the two operands as four halfword 16-bit values. The SMLAD and
SMLADX instructions: 



If X is not present, multiply the top signed halfword value in Rn with the top signed halfword of Rm and the bottom 
signed halfword values in Rn with the bottom signed halfword of Rm.



Or if X is present, multiply the top signed halfword value in Rn with the bottom signed halfword of Rm and the 
bottom signed halfword values in Rn with the top signed halfword of Rm.



Add both multiplication results to the signed 32-bit value in Ra.



Writes the 32-bit signed result of the multiplication and addition to Rd.

Restrictions

Do not use SP and do not use PC

Condition Flags

These instructions do not change the flags.

Examples

SMLAD   R10, R2, R1, R5 ; Multiplies two halfword values in R2 with

                        ; corresponding halfwords in R1, adds R5 and

                        ; writes to R10

SMLALDX R0, R2, R4, R6  ; Multiplies top halfword of R2 with bottom

                        ; halfword of R4, multiplies bottom halfword of R2

                        ; with top halfword of R4, adds R6 and writes to

                        ; R0.