PM0214 datasheet(119/245 Pages) STMICROELECTRONICS

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PM0214

The STM32 Cortex-M4 instruction set

244

3.6.8

SMMUL

Signed most significant word multiply

Syntax

op{R}{cond} Rd, Rn, Rm

where:

•

op is one of:

SMMUL: Signed most significant word multiply

R: 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 Conditional execution on page 64)

•

‘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 or 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.

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