PM0214 datasheet(96/245 Pages) STMICROELECTRONICS

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The STM32 Cortex-M4 instruction set

PM0214

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DocID022708 Rev 4

3.5.13

SSUB16 and SSUB8

Signed subtract 16 and Signed subtract 8

Syntax

op{cond}{Rd,} Rn, Rm

where:

•

op is one of:

SSUB16: Performs two 16-bit signed integer subtractions.

SSUB8: Performs four 8-bit signed integer subtractions.

•

‘cond’ is an optional condition code (see Conditional execution on page 64)

•

‘Rd’ is the destination register

•

‘Rn’ is the register holding the operand

•

‘Rm’ is the second operand register

Operation

Use these instructions to change endianness of data:

The SSUB16 instruction:

Subtracts each halfword from the second operand from the corresponding halfword of

the first operand

Writes the difference result of two signed halfwords in the corresponding halfword of

the destination register.

The SSUB8 instruction:

Subtracts each byte of the second operand from the corresponding byte of the first

operand

Writes the difference result of four signed bytes in the corresponding byte of the

destination register.

Restrictions

Do not use SP and do not use PC.

Condition flags

These instructions do not change the flags.

Examples

SSUB16 R1, R0

; Subtracts halfwords in R0 from corresponding halfword

; of R1 and writes to corresponding halfword of R1

SSUB8

R4, R0, R5

; Subtracts bytes of R5 from corresponding byte in

; R0, and writes to corresponding byte of R4.

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