Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet

147

SAM4E [DATASHEET]

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

Signed Most Significant Word Multiply

Syntax

op{R}{cond} Rd, Rn, Rm

where:

op

is one of:

SMMUL Signed Most Significant Word Multiply.

R

is a rounding error flag. If R is specified, the result is rounded instead of being
truncated. In this case the constant 0x80000000 is added to the product before
the high word is extracted.

cond

is an optional condition code, see 

.

Rd

is the destination register.

Rn, Rm

are registers holding the first and second operands.

Operation

The SMMUL instruction interprets the values from Rn and Rm as two’s complement 32-bit signed integers. The
SMMUL instruction:



Multiplies the values from Rn and Rm.



Optionally rounds the result, otherwise truncates the result.



Writes the most significant signed 32 bits of the result in Rd.

Restrictions

In this instruction:



do not use SP and do not use PC.

Condition Flags

This instruction does not affect the condition code flags.

Examples

SMULL

R0, R4, R5

; Multiplies R4 and R5, truncates top 32 bits

 ; and writes to R0

SMULLR  R6, R2

 ; Multiplies R6 and R2, rounds the top 32 bits

; and writes to R6.