PM0056 datasheet(84/156 Pages) STMICROELECTRONICS

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The Cortex-M3 instruction set

PM0056

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DocID15491 Rev 5

Operation

The MUL instruction multiplies the values from Rn and Rm, and places the least significant 32

bits of the result in Rd.

The MLA instruction multiplies the values from Rn and Rm, adds the value from Ra, and

places the least significant 32 bits of the result in Rd.

The MLS instruction multiplies the values from Rn and Rm, subtracts the product from the

value from Ra, and places the least significant 32 bits of the result in Rd.

The results of these instructions do not depend on whether the operands are signed or

unsigned.

Restrictions

In these instructions, do not use SP and do not use PC.

If you use the S suffix with the MUL instruction:

•

Rd, Rn, and Rm must all be in the range R0 to R7

•

Rd must be the same as Rm

•

You must not use the cond suffix

Condition flags

If S is specified, the MUL instruction:

•

Updates the N and Z flags according to the result

•

Does not affect the C and V flags

Examples

MULR10, R2, R5; multiply, R10 = R2 x R5

MLAR10, R2, R1, R5; multiply with accumulate, R10 = (R2 x R1) + R5

MULSR0, R2, R2; multiply with flag update, R0 = R2 x R2

MULLTR2, R3, R2; conditionally multiply, R2 = R3 x R2

MLSR4, R5, R6, R7; multiply with subtract, R4 = R7 - (R5 x R6)

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